I repaired the frame on my 1998 model and have the process posted here.......
Frame rust repair
The older models are similar, but may also need floorpan support. Call around some shops who do welding and get an estimate. If the car was bought cheap and you will need to dump $500.00 or more into it to fix it, it will pay for itself in fuel savings in a matter of months. If you don't feel safe doing this, then cut your losses and sell it.
Where are you located?