It's an easy conversion. You obviously would need a new bbl and then a new bolt handle. It operates on the wieght of the bolt assembly so having the differnt weight bolt handle gives the mass required for the different cartridge. The .17 HMR can only be made using the 10/22 magnum action while the .17M2 can be made on the standard 10/22 action. I've made a .17M2 conversion myself using an ER Shaw bbl and a MR bolt hanld. can't comment of it's operation as I'm not quite finished - gotta mount optics. For a LOT more info go to www.Rimfirecentral.com it's THE home for anything and everything 10/22 related. Go there, read, search and read some more and all your question will likely have already been answered. A thread in th "Ultimate" section of 10/22 discussions has a long thread with a LOT of members finished projects to give you ideas.
Here's a few of mine:







Have 1 more in mid completion,3 more stocks for builds and at least 2 more planned after those are done. It can be very addicting!