ok, so, for a novice with $600 and recording on computer and looking to get the best bang for the buck, this is what i'd do:
get a m-audio DMP3. this preamp will give you 2 channels into the computer at a time. it'll run you around $150 and resale value is pretty good when it comes time to upgrade.
get a pair of lower-end SDC's (MXL 603's, oktava MC-012's, etc). these'll run you about $150. use these on the acoustic and record it in stereo. i use the 603's on my (all-mahogany)
Martin D15, and they sound excellent. ymmv.
get a studio projects B1. this will run you $80. this will give you a solid amp mic, as well as one that will work decently on acoustic and vocals (maybe).
with the other $220, i'd seriously look at auditioning a vocal mic in the $200-300 range. there are a number of them. an even better idea might be scrapping the B1 and saving up a little more for an Audio Technica 4033--they run between $250-400 (depending on new, used, etc), and are very solid performers on amps, vocals, acoustic, you name it. although, like has been said, vocal mics are very subjective to the voice.
at this point, i'd stay away from a mixer, unless you really need the ability for more channels (which will also require upgrading your soundcard), more complex signal routing or the ability to use it while playing live. the preamps you get in a DMP3 will be better than what you'll find in pretty much any sub-$500 mixer, and if quality is what counts, there ya have it. mind you, the 1202 is a decent entry-level mixer, but for the same money, you can get better quality (the DMP3).
i assume, of course, you've already got recording software. ;-)
next up when you have more cash will be monitors (you really DO want to realistically hear what you recorded, don't you?

), maybe a headphone amp and some great headphones for tracking, a compressor or two, better mics, better preamps, some room treatment, even better mics and pres.....you DID say you had $6000, right?
seriously, for $600 you CAN get decent sound into the computer, and this is a decent start. realistically, you should look at around $1000 to have a "usable" entry-level signal and monitoring chain (don't underestimate the need for monitors). you'll find that your next piece of gear will likely be an RNC (FMR's Really Nice Compressor) for $175 and a set of powered monitors, and it's all a down-hill money sinkhole from there.
cheers,
wade
PS-- i started out on this very same path a little over a year ago, looking to record "acoustic and vocals and maybe an amp" and i have since invested roughly $5K and have expanded my requirements to "recording a full
electric band playing live"......it really never ends--especially once your friends find out what you're doing and want you to record them too......