Transmission shot

96 Lumina APV witht he 3.4 liter, 140,000 miles. Ran fine until I heard a loud bang & grinding metal. After that, no gears but 1st, no reverse either. Transmission fluid looks as if it's filled with glitter. I'm pretty sure that means it's shot. There are other issues with the vehicle & I'm trying to figure out whether or not it's even worth it to get it towed to a transmission shop for an estimate. I'm looking for a very broad idea as to how much this might cost to fix.

A rebuilt 4T60E would cost about $1,800 (plus core) in this area. I have no clue about the average cost in your area. I would not recommend installing a used transmission without going through it and freshening up the frictions and wear areas before installing it UNLESS all you intend to do is restore the vehicle to driving condition ans selling it immediately.

Driving it any further will likely cause more damage and more $$$. I'm guessing the output planetary/differential is eating itself, but that's only a guess since it's very common. Most people don't use parking brakes and that is the common result.