What range of cost to fix worn front suspension on 04 montana?

the dealer is having you on
thumps , bumps and the like indicate something worn , loose or ready to go bad quick
it could be lower ball joints, upper control ball joints or upper mount if strut suspension
could be worn rubbers in the stabilizer bar area
Best take it to an accredited suspension specialist shop and have it checked out ( get a quote to fix) before it fails and causes serious damage
if it is serious and costly get a report and then front the dealer for the cost of repairs or talk with a lawyer

Your air shocks are not working
you should have an air pump in the back end of your car which pumps the shocks up but the pump may be worn out as well the air lines may have holes in them. If the pump is working you will hear a humming as the pump works.
My pump was shot and my shocks were worn out so I replaced them with manual air shocks you pump up with an air compressor with the hose coming out under my bumper out of sight. I check them every six months and top them up. Sure cheaper than buying the pump and all the trimmings.

well you must have a problem with your power steering, or the front suspension components involved in steering are locking up. take it to a dealer and ask for an estimate to fix it, then take that estimate to a private shop and ask them how much to do the same work if you buy the parts yourself at advance or autozone. the thing is coming up on 10 years old so it is going to be needing repairs more frequently.
people die when the get worn out, cars end up in scrap piles, nothing lasts forever.

possible worn suspension rubber mounts, worn tie rod ends
take it to a suspension specialist shop for a check of the front end

The frame can be "straightened" to put the suspension attachment points back to the proper location by a (larger) body shop. Cost may exceed the value of the explorer though.

If your car is about 10 years or older chances are that the front rubber suspension components are worn and rubbing agaings their housing. There are at least 4 areas for each front tire that could be worn: Strut housing, control arm bushings, center control arm bushings, or stabilizer bar bushings. There are ball joints that can wear too, but usually do not make noises at a standstill. My suggestion is to go to any tire store and have them look put the car up on a rack for a thorough inspection. Most people let these parts go for too long and the cost gets high to replace. You obviously are very careful with your car so this should be a routine suspension fix for the garage. Good luck.

It could be that the pipe from the air pump is defect it could also be that the air spring ( strut assembly ) is broken.

STAY AWAY FROM THIS CAR!!!! If there is a high piched whistle from under the bonnet and it is a turbo the said turbo is about to let loose. As for the other work niggley electrics are not un common on the passat all the other work seems wear and tear but these cars are not killed off easily it sound like it's a lemon Please dont buy it unless you are married to the owner of a bank.

Something is wrong with the front end. Bring it in for a front end alignment (that could be all it needs) and have them check for problems with front end suspension components. There may be something that is worn out ( such as ball joints, or tie rod ends) that is causing the uneven tire wear. There may also be a problem from hitting a large pot hole, or curb, which bent something causing this. Tell the shop to NOT align the front end if they find that some components need to be replaced, as when something is replaced, you should have the front end aligned, and you don't want to have it done twice.

The brake pads or rotors are worn or the tires could be worn.If you apply the brake and let off the steering wheel and the car pulls left or right i would suspect the brakes/pads,if not you may have an suspension issue in the front.