Have you got experience rebuilding rear ends? It's not a job to be taken lightly, it requires a lot of careful measurement and adherance to instructions. You can cut the cost significantly by doing it yourself, but I don't want you thinking it's as simple as taking out the old and tossing in the new and being done after a couple hours. I had a shop do my gears, full rebuild, new seals, ford racing gears and rebuilt the carrier with new LSD clutches. Cost me a premium at $900, but it was done in a day and it came out perfectly, the shop knew their stuff. Also take into account that you'll either have to get a piggyback speedo recalibration tool(~$150) or a tuner(SCT/Predator etc. ~$300) to reprogram your computer for the new gears.
Aside from that, all the parts trinity suggested are top notch.