What type of transmission fluid should I use in My 2003 GMC Sierra 2500 HD Diesel truck?

hope this helps? should do it for you.
https://www.justautorepair.com/multimedia/1-belts-diagrams/detail/129-diesel-belt-routing

check both your fluid levels and the programming for the tranny, if it's electronic. 195K means you should probably look at a fluid swap and possibly any tranny filter

No,it won't.

rebuild time, shift solenoids-Denny

It usually takes five quarts of transmission fluid if your replacing the filter. If the transmission is completely empty, such as a new unit, it takes about ten.

You probably have hydroboost brakes and that system is powered by the power steering unit. If you have no steering and brakes, the first thing to check is the power steering pump. Check for low/no fluid. If the fluid is okay then the pump might not be pumping and you will need to replace it.

gas or diesel ?

Problem with Diesel Fuel System. Gmc 2002 duramax 2500 HD 4x4 will start 

try checking your neutral safety switch.

check owners manual,or call a gm service dep.