if you supply the transmission, you can get a shop to pull the old one and replace with the newer one for cheap if you can find a good shop. when i had the clutch in my eclipse replaced, it was 300(albeit i supplied the clutch) for them to drop the tranny, put the new clutch in, resurface the flywheel, and put it all back together, and took them 3 hours.
and i would shy away from doing it yourself. ive done several tranny swaps on fwd, and decided that, even though its my car, id rather pay the 300 bucks than take all weekend, and know its not only done right, but if anthing messes up, i can take it back.
1994 Tbird 4.6l, 3 trannies later and still bone stock.
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2002 Stang GT, 5spd "Ellie", Eleanor Tribute. Stage 3 Roush Kit, Saleen S281 Spoiler, JMS / Ironman Customs CL-2 C-Pillar Panels. Black Racing stripes on Pepper Grey. Minor Bolt ons, Real mods coming soon(Procharger, VT cams/Headwork, 31spline Eaton Rear, T-56 Swap)