I have a 2000 toyota celica gt auto transmission. Can I put a 2000 toyota celica gts manuel transmission in it?

why not.

I suppose anything is possible, but, the cost to change this is going to be so much, you would be better off getting another car. Just my opinion. You'll never get your money back when you sell it.

While I like the sleek look of the 2000 model year Celica (I was tempted to buy a GTS), there's no way that I'd invest the $$ in a tranny swap, if I was in your situation. I can understand why you want to do it....140 HP in a AT car isn't especially quick. I would sell it (resale values are pretty good on them) and maybe get a used Scion FR-S with MT? It's a great car too!

So, Justin, are you convinced to skip this now. Have you considered a Subaru WRX STI? That's a great performance car and you'll be impressed. Check this out, of course, there's used ones as well. http://m.caranddriver.com/subaru/wrx-sti