Hi, and welcome to the group!
It would help us to know your budget, but to start out, you need neither mixer nor separate pre-amps. You need a multi-channel interface. These have pre-amps built in and a FireWire connection to your computer that can transfer all the channels at once. In this way, you end up with individual tracks on the computer disc that you mix in software to a stereo track that you burn to CD.
There are plenty of reasonable-quality 2, 4 and 8-channel interfaces to choose from. Most of these have at least two outputs as well, which you will need to drive monitor loudspeakers.
If you are thinking of getting ProTools, you are very constrained as to the choice of interface. If it's to be ProTools LE, you have to use DigiDesign interfaces. It it's M-Powered Pro Tools, then you have to use M-Audio hardware. In addition, you should choose a computer from the list of supported types for ProTools. There are plenty of programs other than ProTools that will work as well if not better for your purposes and do not constrain your choice of hardware.
So your shopping list should look something like:
Vocal microphone (SM58)
Instrument microphone (SM57)
Multi-channel interface (2, 4 or 8 channels)
XLR-XLR microphone cables
Pair of powered (active) monitors with cables
Computer with FireWire interface and two separate hard disks
Acoustic treatment for your room
All these items have been covered in depth in this forum in the past. The search engine is your best recourse.