I Got a Big tranny Problem

I just got a 97 mustang GT I'v been horsing around with it until something went wrong! It's in first gear. I can pull it back to secong gear and it feels like there is nothing there but I feel 3rd,4th and 5th. When put in nuetral it still acts like it's in first. When I try to put into reverse it won't go nowhere. It acts like it's in first and in reverse and is fighting each other. The mechanic I talked to said he thinks some kind of pin in the shifter assembly has been sheered or broke off and that is causeing this. A friend said could be shift forks are bent or broke. If anyone has had a problem like this please help this is my first mustang and im stumped

ok i hopefully find out tommarow what is broke. if shift forks are broke would a tranny out of a stock 01 cobra be a good replacment? if so what would i haft to chang to make it work? im really workn on a tight buget. does an aftermarket shifter help with the problem that occuerd with my tranny?