The double blades are for purfling channels on violin edged instruments that do not have binding, however, you can use these gramils with a single blade with no problem. Router bit and bearing is great, but that's going to depend on whether or not the top and or back are domed. If they are, then you're going to get a varying width of rabbet as the router tilts out to different degrees at different places around the rim...
Some of this stuff you just have to do and screw up to understand. There is no teacher like failure and then the inspiration that comes when you figure out how to fix your mistake. If it's all handed to you on silver plate, you'll really be in deep sh.. when Murphy does come to visit.
If this is your first time doing this stuff, just start with simple binding. Get that right, and then move on to binding plus purfling. You can also get multi-layer binding that takes care of purfling lines.
There's nothing like that first 10,000 hours of doing anything to put you where you need to be in the expertise arena, but you're not going to build like an expert by not trying things and being afraid of screwing up. Also, there is a massive amount of information on-line, in books, and in videos on all of this stuff. We shouldn't have to reinvent the wheel here, nor have to write about the process. It's all at your fingertips. Don't be lazy; do your homework. And don't think there are significantly better or cheaper ways to do any of these tasks than are presented in all the resources. Tens of thousands of hours have gone into figuring this stuff out, and in spite of at least one recent participant's disdain for the body of knowledge of lutherie, the collective knowledge is pretty good...and available.