automatic transmission

I have a 1994 Oldsmobile Cutlass Supreme. Recently, I have been having transmission problems. What it is doing is, when I come to a stop, it is not dropping completely into first gear. I have to sit and shift it into neutral or reverse, then all the way back down to 1st to get it to properly pull out. Can anyone out there tell me what the problem could be and how expensive it will be to fix?