My Sierra (1998) has a 26 gallon tank. It's the short bed. If the truck has the long bed, then it has the 34 gallon tank.
Not yet on the remote trans filter. Still a bit too cold, and I need a dry place to work on it. It'll probably have to wait till the big thaw. I did manage to put new spark plugs in, and while it was in at the shop getting a new outer passenger door handle installed, I had them replace the fuel filter. The fittings were so rusty and stuck, I couldn't do it. Also had a general inspection, and all was well, except a little low on the rear end fluid.