I have never built a thing related to MAME, and although I own 11 arcade games, I really know almost nothing about what makes them tick either. How's that for a solid basis to start a MAME project on?

I have wanted to try this for awhile, and decided to just do it. My problem is that there are all these great "here's what I built" projects all over, but they are all different and it's really hard for me to make sense of them. So, let me tell you the very basics and see if you have a guess of what directions to 'follow' for my cabinet.
I think I will use my exisiting Die Hard (Sega ST-V JAMMA) cabinet. Although ST-V, KLOV says it is JAMMA, so if I understand MAME controls so far, I could easily just hook the JAMMA connector up to a J-PAC, and thus save all the hassle of control panels. Is that right? I also know that to use the 25" monitor in the cabinet with a computer, I need some kind of adapter to hook it up, plus change a setting somewhere (the number 15 rings a bell - 15 hz or something? - LOL!).
So in other words, it will be a very simple build this time. I'll use an old computer in my attic to start (like a PII-400) just to get everything working. Then if it all works, and after learning as I do this, I can either start upgrading this one or build a more complicated one.
Okay, so now you know what I'd like to do - is this about the simplest setup to start with? Any leads on where I can find some step-=by-step directions to start this project now? Everything from "buy this" to "hook this up here" to "download and install this"

Mark