dsella, while I applaud your enthusiasm, I think you might need a little shove towards reality as far as your business idea goes. There's nothing wrong with wanting to do what you were thinking, but the real-life logistics of it aren't as easy as "build computers --> ship computers". Like it or not, big-brand companies have the hardware market cornered; this isn't my opinion - it's simply fact. They are able do spit out thousands of systems across all price-ranges for a fairly consistent hardware-based profit margin. Because of that, it really isn't feasible for someone who does custom builds (unless you want to cater to a very specific niche market, in which case, chances are, the customer will already know what they want and have the skill/know-how to do it themselves, or someone else who has been in the market for a while will have already beaten you to them).
If you want to get into this business, soak up every ounce of information you can about the entire business (hardware, software, etc.). The vast majority of my business comes from servicing systems and software-related issues. Maybe 5% total comes from building actual systems, and that's only for my Home Clients - with the Business ones that probably drops to less than 1%. In short, the money simple isn't there as far as custom builds go. Sure you might get a system here and there, but nothing even remotely close to live off.
Please don't view this Post as an attack or bash, but rather as a 'hey, I'm not sure how serious you were about it, but take a few minutes to see the full picture and not get any false hopes' type.
As far as Geek Squad goes, it's hit or miss depending on where you work and the skill level of the others there - Firedog is the same thing. Granted, every once in a while you'll have someone there who's super-skilled and just biding time while finishing up school or while they're trying to grow their own business, but the majority seem to be folks that really aren't that great with computers in the first place - they just happened to know more than the other guy who applied. They follow a specific set of trouble-shooting steps as dictated in their little book. If the problem isn't resolved by the end of those steps, it's hit-or-miss as to whether or not they have the reasoning to dig further. Also, make no doubt, they are salespeople first, <cough>repair technicians<cough> second. It's their job to sell people products and services, not jut fix a system.