1999 Toyota Corolla worth fixing?

Check the fluid level in the transmission, If none or low you can either rebuild or replace with used one.

I would get a used one and replace it. Check prices at local junk yards and installation prices at local garage's.

You are probably looking at $300-500 for the tranny and $700-1000 for install. Just remember that any garage that installs a used tranny will not warrant it, the junk yard warranty will be replacement only, not installation.

If you can find a local mechanic willing to do it in his garage, you may get it installed for $500 or so.
I installed an automatic in a 1991 for $500 and the guy paid $350 for a used tranny.