Having had two gear installations go bad, I'd sell the gears on Facebook, Craigslist, eBay, etc. & have the installing shop provide them so there's no chance of any kind of a warranty issue where fingers would be pointed back & forth.
Of course the shop will warranty their labor. But here's the issue. What happens when that potential problem happens? The installing shop will of course confirm they did the installation correctly so they'll blame the parts you provided. Allen will (more than likely rightfully) blame the installer for screwing the setup/installation up. If it's the fault of bad gears (unlikely) and Allen sends you new gears, the shop isn't going to reinstall them for free since they will claim they did their job properly.
The bottom line is you're opening yourself up to being caught in the middle. If the shop provides both the parts and the labor you would have zero issues getting them to take care of any possible issue with zero problem.
Of course the shop will warranty their labor. But here's the issue. What happens when that potential problem happens? The installing shop will of course confirm they did the installation correctly so they'll blame the parts you provided. Allen will (more than likely rightfully) blame the installer for screwing the setup/installation up. If it's the fault of bad gears (unlikely) and Allen sends you new gears, the shop isn't going to reinstall them for free since they will claim they did their job properly.
The bottom line is you're opening yourself up to being caught in the middle. If the shop provides both the parts and the labor you would have zero issues getting them to take care of any possible issue with zero problem.