Transmisson Problem.

I have a Turbo 400 and a Torque converter that were built by a company named Select Performance in New York I believe. I have no idea how long ago as they were on the car when I bought it. When I first started driving the car late last year all was ok. Then I had a car show and on the last day of the show when I went to leave I put the car in reverse and nothing. I turned the car off and turned it back on and it went into gear and off I went. I did notice that the car did not shift as hard but thought nothing of it.

Fast forward two months till today. I bought a new Trans pan and I wanted to install it. I had to change the oil pickup as this pan was a bit shallower. I put everything back together went to go cruise around the block and I put it in reverse and nothing. the engine does not even idle down like it is in gear. I reved the engine a bit and nothing. I know nothing about Transmissions but what do you guys think it could be? Money is definitely an issue, but I imagine that I will need to take it to a trans shop.