1998 Cadillac Deville transmission

Just got the car. Person I got the from said it was not shifting good and was giving a code. He had the code check at a parts store and they said it was the shift solenoids. So I was going to replace them myself so I drop the pan and it was clean no metal in the pan. But then found out you have got to drop the valve body and take it apart to get to the clips that hold them in. So I took it to a shop and had the 1-2 and 2-3 solenoids replaced at a cost of 200.00 they said that the solenoids did not fix it. They said 2ed gear was not working only 1st -3ed
and overdrive and it needed to be overhauled at a cost of 2.000.00 dollars. I drove the car home from the shop only one mile and it would not shift out of 1st gear. So when I got home I took the cable lose from the battery and reset the computer. It then seem to be shifting ok. But I cant tell if it has a 2ed gear or not. It seems like it shifts a little harder from 2ed to 3ed then any other gear but I not sure if it just shifting from 1st to 3ed and there really is not a 2ed gear or not. But even with all that it will drive great for few miles and after I get up to about 45 miles hour then come to a stop the engine light comes on and when I go to take off it will not shift out of 1st gear. So I reset the computer and then it will shift fine. Could this be the converter solenoid bad? Or the over drive clutch slipping a little? I have not done the brake test yet to see if the converter is locking out by watching to see if the R.P.M.S jump up when I tap the brake to see if the converter is locking out like it should be.
Or to just drive it in 3ed gear at 45 to test and see if the engine light still comes on when not in overdrive. But I will test these two things tomorrow. But do you know of any other things that may be wrong that I should check? And how can I tell if there is not a 2ed gear? Not sure I believe this shop. And way is it not shifting out of first after the engine light comes on until I reset the computer? Is this some can of safety feature? From what I have read outside of the two shift solenoids I have already replaced there is a solenoid for the converter there is a pressure shift solenoid and a speed solenoid all are hard to get to. And cost a lot in labor to have replaced. I have read this 4t80-e transmission is a really good strong transmission that GM used for 10 years in many cars but these solenoids going bad is a real problem on them at around 100.000 miles. And there is so many of them. And all of them are hard to get to and replace. So it cost a lot to get them replaced. I only paid 1000.00 dollars for the car the blue book is only 1500.00 dollars so I cant see spending 2000.00 dollars to get the transmission overhauled even thou I really do like the car. Not sure if to flip the car and let someone else worrier with it or not. I have been out of work for 6 months now and don't have 2000.00 dollars to rebuild.