SHOULD I CHANGE GEARS MYSELF? (LONG)

[LOCASH]

O.K. I know this topic is on here once a week but this is different. I live in Italy right now and I am taking my car to a shop that does rally cars to swap gears. I am quite sure that the guy has never seen an 8.8 before so he will be doing it for the first time. I have a bit of experience as a parts hanger at a garage and I have done all of the mods so far myself. I have done alot of research and I have the Richmond Gear video. I could recite all of the steps from memory but I have never actually done it. I have a friend who has the $170 set up kit. Should I try it myself or take it to this shop?

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86 GT T-tops, AOD, B&M shift kit and hammer shifter, ROH wheels, K&N, Timing,MAC headers, 2.5 off road H, 2.5 American Thunder, 87 spindles, rear disc,SS lines, BBK 1.5, poly bushings, Crutchfield front kick panel speakers.
"DRIVE LIKE YOU STOLE IT!"