Is it worth it?

I have a 95' Galant S and the tranny just quit at 150000. So I was wondering would it be worth it to go out and buy a used tranny (Either put it in or have it put in) or should I just sell it as is. According to KBB the as is value of the car is $1550. I'm asking $1000 now. Also would it be possible for me to put in the used tranny?