I Hope You Can Help, Need advice on software, hardware Options

[eleeguy]

Hello Everyone,
I tried to do some research on the below. I even read the MacMusic articles and ended up confused.
Some background: My 17 year old daughter wrote her first song and taught herself a couple of chords on an old guitar for a mother's day present, in 2000. Still completely self taught on the guitar, since then she has written & composed about 15 songs, won 4 different contests and opened for a few local concerts. (I was going to put her website here, but then I remembered the rule about no advertizing). She has been encouraged to pursue a career in music. She is graduating high school this year and intends to take the next year off to pursue her music career.
I want to get her set up to do some recording on our computer. I currently have a Power Mac 7500 with 88 Megs of RAM and a 604e processor running at 180 Mhz. We have the stereo audio imput and output jacks. I also do not have a USB port installed.
The short term goals are to have her record her singing and guitar (acoustic/electric) and refine those recordings a little. In the shorter future, it would be nice to be able to record other instruments and voices as well. Longer term is to be able to do home studio recordings, mixing, and mastering. (I hope I'm using the right terms).
So, I'm thinking that the software should be basic enough to be easy to use now, but such that there are more sophisticated versions for the professional stuff later so everything would have to be re-learned. We are very budget concious. We would rather spend more money later on upgrades and add-ons, when needed (including better computers).
So my questions are:
What software would you recommend?
What cards or hardware do you think we need?
Would having a video mirroring card and a second monitor be advantageous?
Can you suggest anything else that would be helpful?
I really do appreciate being able to post this and I am anxious to see what feedback I get.
Yours truly, eleeguy.