I definately agree that you want to stereo record your acoustic guitar. I'd look at MXL 603 or 993 pair for the guitar. About $100 for the pair. I got some pretty sweet recordings out of the 603's myself.
I had the MXL 990 and it is good for $50. For a few more bucks, I'd recommend the Studio Projects B1 thumbsup. I have that one, and it is way better than the 990. I got my B1 for $70 on craigslist. If you want your vocals on a whole other level, Shure SM7b

. Can be found for about $250 used.
For the interface, if you are planning on recording the guitar and vocals seperate, then you only need a 2 channel interface. There are dozens to choose from. I like the Presonus Audiobox or Firebox and can be had for $150-200 new. If you want to record all 3 mics at once, you need a multichannel interface. The UX8 is $300 right now at GC and MF.
So thats about $320 (if you go with the B1 and a two channel interface) for three mics and an interface. Leaves money for XLR cables/Headphones (HD280!!!!!)/mic stands/pop filter/etc. etc.
Have fun!