REbuild shop?

I have a 92 stealth that the tranny is gone i think. It will drive normal untilk i hit about 35-40 mph then it just revs up. any ideas? if it is shot anyoen knwo a good shop in Colorado that is moderatly priced to rebuidl it?

also if anyoen in colorado knows how to convert a Auto trans. to manual trans please let me know

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