Just ran across this while I was reading your post,
MSI FM1 AMD A55 Motherboard and AMD A4-Series A4-3400 APU and Corsair CMX4GX3M1A1333C9 XMS3 4GB DDR3 RAM and Corsair CMX4GX3M1A1333C9 XMS3 4GB DDR3 RAM Bundle at TigerDirect.com
Keep in mind about matching socket fittings for the motherboard and processors. When I built my first computer (Back in 2000), I was in your same situation. My first summer before High School and my mom gave me a blank check for a computer. I knew the basics, AMD and Intel required different types of motherboards, but I figured it was a one type fit all. Needless to say I was quite angry when I broke the processor after trying for 15 minutes to get the pins to fit, and figure I just wasn't pressing down hard enough.
Selecting the Motherboard-CPU combo search filters will prevent that situation, additionally you can usually get a better deal. Also, when applying the thermal paste, remember a little bit will go a long way. I remember I had a problem in that field as well, I believe I had just finished reading horror stories about over heating issues and frying chips. So after the whole having to buy a 2nd processor deal, I knew I couldn't afford any more accidents. I forget exactly what happened next, but I remember having to take the whole thing apart and when I unmounted the heat sink, the thermal compound had oozed out the edges and started piling up on the motherboard. All was well after about an hour of cleaning with q-tips and isopropyl alcohol.
One last thing, make sure to ground yourself before touching any of the pieces. I ruined another motherboard early on in my building days by handling one repeatedly while working in my carpeted bedroom with socks on.
Sorry to go a bit off topic, I know you only asked about AMD vs Intel, but I figured a couple tips couldn't hurt. Best of luck with completing the task at hand though Malcom, keep us updated with what you eventually decide on and perhaps some pictures of the finished product.