No forward engagement in drive position

Based on the symptoms you described, it sounds like there may be an issue with the transmission control module (TCM) or the transmission itself. It is possible that the TCM was damaged when you accidently forgot to fully engage the connector on assembly and touched it, which caused the doors to lock and unlock multiple times. This could have caused a problem with the transmission's ability to shift correctly.
To troubleshoot the issue, you can try the following steps:

1. Check the transmission fluid level: Make sure the transmission fluid is at the correct level and that there are no leaks.
2. Check the transmission filter: If the filter is dirty or clogged, it can cause shifting problems.
3. Check the transmission control module (TCM): The TCM is responsible for controlling the transmission, so it could be causing the issue if it is damaged or not functioning correctly.
4. Check the transmission itself: If the problem is not with the TCM or the transmission fluid, there may be an issue with the transmission itself. This could be caused by a problem with the gears, bearings, or other components.

If you are unable to diagnose and fix the problem on your own, it is recommended to have a mechanic or dealership technician take a look at the car. They will have the necessary tools and expertise to properly diagnose and repair the issue.

Have you checked the fluid level in the left side?

My Econoline 250 with 4.2 lost fluid from hose leak, fixed leak everything was normal for 3 days till I drove it on highway. When it went into overdrive lost forward power. Turned off OD and did ok for a while. Lost forward gears slowly, put in fluid, hard to tell when full. Reverse is fine but have to rev up engine to get forward to engage, then everything is fine at lights and such till take out of drive, then have to rev engine to about 2500rpm to engage drive. Help?

I would have it towed to a different shop for a second opinion.
To start at the beginning, if it works in reverse but not drive the linkage is working.
When you put the transmission in low or second you are bypassing most of the sensors and valves. You put it in first or second gear and it stays there.
It could be a long list of things from the valve body to the pump to a solenoid or sensor.
There is a good chance the problem could be fixed without needing an overhaul.
You never take a knife to a gunfight, so you wouldn't have anybody but a transmission shop work on a transmission.
When they recommend an overhaul, they are pulling your trans out and replacing it with someone's rebuilt out of the crate. No worries on their part.

Put the vehicle in Park, disconnect the shifter from the shift lever on the trans, adjust the linkage or cable so the connection is clearly a slip in/on connection and tighten things back up. Hopefully this will solve your non-reverse. As for all the gunk and metal shavings, friend, you better have another tranny standing by in your garage when this one stops working completely.

You could and should have changed the fluid,so
it is clean
Add a bottle of RED LUBGARD

Next thing to try is cleaning the valve body
as it has sediment in it and the cold temp
as well is hanging the valves

The bad part on almost all trans valve bodies is that
half the system is in the case and you lose the check
balls working in the vehicle.
You will need a schematic of balls positions so you
can stick them up there with vasoline or trans gel,
then install the valve body

After that you pull the trans and to the same with
the pump or just rebuild it

The weld on the manual lever is known to break loose. First, with the wheels off the ground, with the lever in the park position, does the drive shaft lock in park? If yes or no sometimes, drop the trans pan. I bet the nut on the lever camd loose.

it sounds like the problem started with the brake shift iterlock switch by forcing it he now broke the trans shift cable mech at the column

No movement in any gear: pump failure, or total loss of fluid. R&R, or refill pan and find the leak. If out of fluid, avoid running the engine until the trans is refilled to avoid pump damage. To check for pump failure, check fluid level with the engine off, then start the engine and recheck fluid level. If level does not go down when engine is running, the pump is broken.

No forward movement in OD or D, but L2, L1 and R work: Forward sprag is broken. R&R. Try not to run or drive the car or further damage could result.

Put a line pressure gauge ($55 shipped on Ebay, or visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.500" boost valve (easy fix in pan).

Good luck and try pulling the ECM and transmission fuse out with the ignition key in the on position, "engine not running" and placing it back in after 10 seconds and start the engine. If it's a PCM problem, this will reset it.

Forward drive in the C6 requires both the forward clutch AND the low/reverse, one-way clutch, or intermedaite band to engage. Since you have reverse but no forward, the forward clutch is most likely the problem, since it is needed only for forward speeds and does not affect reverse. Sounds like a trans rebuild.