Tranny or engine problem and best way to fix it?

What is your question?

My car has had transmission problems since about 90,000 miles. Had it worked on twice and have had the engine rebuilt and STILL have problems. Right now, my AT light and check engine light are on, before it was just slipping, now it wont shift out of second. Happened about a year ago but had the codes reset and didn't have this issue until now. Tried to reset them again but it didn't work. Is this a tranny problem or an engine problem? And what's the best way to go about getting it fixed?