i havnt made the 2.73 to 4.10 jump, but i did make the 2.73 to 3.73 jump in a manual and it was awsome, the best mod i ever did. It is a whole new car. You will love it in your car. Gears is the best mod you can do for your car for the buck. Those 4.10's and that shift kit, that car will dip.
Do it yourself man. Its fun and you learn alot. If you have a good video its not hard at all. You need some special tools but its not bad. I got the D&D rebuild kit for my tranny and it has all you need as long as you dont need any new gears or sliders.
A home mechanic can do it. Ive dont it. WHile its out of the car replace bearings and rings at least. If piston rods and crank is in good shape reuse it. But when you tear into an engine there is no telling what suprises you will find. Remember too that 5.0's came stock with forged pistons...
That is the throw-out bearing, shoot some grease on it and around the area, if that doesnt work drop the tranny and bellhousing and check the bearing retainer on the transmission, that might be messed up. Just look for things out of the ordinary.