BMW Repair: 87 bmw 325is only shifts into reverse, bmw 325is, 1987 bmw 325

Question
I recently bought a 1987 bmw 325 is with 160k miles from a friend at work for 200.00, He changed the transmission fluid in it against his mechanics advise, he told me that he drove it for about two weeks when finally it wouldnt go in any other gear but reverse.  Do you think that the transmission will have to either be rebuilt/replaced, and is it worth it? How much damage do you think it did to the transmission. thank you

Answer
I don't understand why he would be told not to change the fluid by his mechanic,although it is strange happening.At 90k the tranny fluid and filter is changed so being done at 160k is early for the second time around(assuming there was regular maintenance done).Now why only reverse?Did he just change the fluid or did he replace both filter and fluid?It is a 4hp22 tranny so it CAN be changed.That would be my question to you is, was the filter changed as well?If the pan was not removed then I would check it to see if there is any debris in the pan.
I look  at it this way you only spent 200 dollars on a BMW 325is,Mileage is low for the year and miles.It maybe(I would try)able to find another tranny if that indeed has failed.If the body is in good shape,interior not to bad spend alittle and keep it.The 4hp22 transmission was in many of the models.