1991 Chevy Lumina is dying!!! Please Help

I purchased a 1991 chevrolet lumina in may of 2004. it now has 140,000 miles in jan 2005. i believe that i may have a head gasket dying as i keep blowing heater hoses. Also on a recent road trip, my five speed transmission started to get hard to shift. It turned out that the transmission had a leak and ran dry... my bad. After oiling the transmission i regained shifting abilities, but shifting is not nearly as smooth and also i lost my fifth gear synchro. The transmission also howls now and i believe it is on its last legs.
So what i would like to know is... has anyone ever seen another 91 lumina z34 with a five speed? All the others ive seen have been automatics.
Also, does anyone know where to find a replacement for this transmission? Or will the transmission hold up with a little tlc? Im a college student so money is extremely tight, but i do have a backup vehicle that i can drive, though it gets 12 mpg... so if i do my own work it'll need to be over a short period of time.
Also, are head gaskets a pain to change out on these motors?
Finally, should i just sell this POS and start over? Its a super fun car to drive but its been fairly unreliabe.

the transmission shouldn't be too hard to find. If my mind serves me correctly, the 5-speed in those is just a tremec 5 speed, and I believe it was in a bunch of GM's those years. The head gaskets are a big job, and a bit of a pain in the ass, especially when it comes time to re-install the timing belt. If you have some skill and tools, it can be done.