Microphone for basic recording

Here's a basic recording question.

I want to do some simple recording, mostly recording a large # of small (2 minute?) guitar (and a few voice) clips off my guitar amplifier, and catalogue them. My P3 box has Soundmax integrated digital audio, which is likely low end, but adequate for my needs, which is to end up with a catalogue of my own guitar studies for reference, not for "audio listening" as such.

Software: I'm looking at Audacity, Total Recorder, and Freecorder (a new entry with ads showing, but no spyware.)

But the QUESTION is, what do I do for a microphone. I have an old AKG mic, which is a good old (1970s) dynamic mic. So, can I run that into a transformer or something, with a regular guitar cable, and then out with the appropriate cable into the computer; or would it be easier and as cheap to buy a modern mic designed for digital recording?

And if it's the latter, how much does such a mic cost for low end work?
(I can get a superior mic later if I decide to record anything serious.)

Thanks for any input { no pun intended :<) }

sd