If you want to assemble your rifle yourself: You will need specialized tools, period. Even for a Remage build, you will need a means to wrench the action and barrel apart - or barrel nut. For me, that means a barrel wrench or barrel nut wrench, and an action vise. Let's be realistic, you're not going to blueprint your action or chamber your barrel on your own, so there's not much sense in buying $700 manual blueprinting and chambering tools, and less sense in buying a machine lathe just for one rifle. To remove a Remington barrel and install a Remage, you'll still need an action vise, a barrel wrench to remove the old barrel, then the barrel nut wrench to install the new one, as well as a means to set the headspace for the new barrel, whether you use a fired case, a factory round, or preferably, a set of go and no-go gauges.
If you want a custom rifle: Order parts, and pay a gunsmith to install the barrel. Depending upon what stock or chassis you choose, you may or may not need to block and bed the action. McMillan stocks offer the option of pillar blocks from factory, chassis' don't need to be bedded or blocked, Manners offers a "mini-chassis" option for some of their stocks. Alternatively, if you go with a cheap laminate boyd's stock, you'll need to block and bed it. Not difficult, but something to consider.
For me, I don't really prefer the Remage nut style, so I'd rather order the barrel and action, pay a smith to install the barrel and time my muzzle device, then I do my own stock work, or order a McMillan, Manners, or chassis which doesn't need block & bed work. I own tools to hand blueprint and finish chamber barrels myself, but for the money, if you're only doing 1 rifle, or even 3-4 rifles, you're money ahead to pay a smith.
(Like, how often does THAT happen?)