i am a guitar player and i would like to record myself playing and singing
A great way to become a better musician.
Why be tethered to a mic, pre, computer, etc. The current stock of portable digital recorders are fabulous for what you want to do. Tascam and Zoom make great portable digital recorders, although I prefer the Tascam models. Simple to use, easy on batteries, surprisingly good fidelity (can record in both WAV and up to 320 kbps MP3), readily available media (microSD; a 2GB card will record up to 14 hours of stereo content in 320 kbps MP3), cheaper than a decent mic/pre combo, and connect to your computer for playback, editing, etc. Or you can plug one right into a powered speaker system (e.g. computer speakers) for playback. Don't rely on their tiny internal speakers for listening.
Try the
Tascam DR-05 to start with. You might just be surprised.