I have 2 of the pre-accutrigger flat back actions that started life as 7mm mag sporters. One still sits as it came from the factory, the other I have a number of different barrels for.

An action wrench and barrel nut wrench are the tools you need to swap barrels out, some here use go/no-go gauges and some don't. I do.

There are a couple of vendors on here that deal with the aftermarket barrel manufacturers. Apache Gun Works, Sinman, and Jim Broggs of Northland Shooters Supply are the first that come to mind.

Synthetic stock options are fairly limited. Both of mine had the factory wood stocks on them, but I did snag a takeoff detachable mag stock from a member here that is on one. I plan to get a Boyd's tacticool or a Choate Tactical for that one at some point.