Call Jim Briggs @ Northland Shooters Supply and he'll give you the low-down on a Rem-Age setup.
Off the top of my head, you're looking at about $400 for a Criterion Rem-Age prefit barrel, NSS recoil lug, and NSS barrel nut and maybe $20-30 additional for a barrel nut wrench. You'll need your action notched for the NSS recoil lug which you can DIY or send to most any gunsmith to do, though Dan @ Dark Eagle Customs does pretty good business doing Rem-Age action work which includes notching for the recoil lug (I think Dan uses his own lug) and action truing.
How hard is it? No harder than swapping a Savage, and the hardest part will be getting your factory 700 barrel off.
You'll also need AT MINIMUM a shop vise, some notched hardwood blocks & resin (or brown sugar) to hold the barrel in the shop vice, a Go-Gauge, and some Scotch-brand clear tape (which you can put 1 piece on bottom of Go-Gauge to make a No-Go.