I honestly believe that the trans needs a rebuild. However if I were in your shoes and had the fluid out and the pan off......I would think that a quick solenoid change and a filter isn't that much to try, the price gap is substantial and would kick myself if there wasn't anything else wrong with it.
Worst case, If it's toast, then pull out the new solenoids and save them for a later date. You can check their operation first though (not sure how) and just try the filter but metal is bad. Another poster just went through the same ordeal and needed another trans.
3-4 gallons of trans fluid is a waste though if it's bad. Tough call my friend.
If when you drive it and you feel a shift into third but so much slipping it won't accelerate.....then don't waste your time. It's likely a goner.