Well, I'd be be more than happy to provide you with a quick howto, but as I said in my first post, it's been a while since I made the thing, so my memory may have faded a bit on some points. Also, I have found that there are better ways of doing things. Like using a RAMdisk and a readonly filesystem so that it can be switched on and of at all times without fsck running at startup.
But anyway, here goes.
I started the project when I got some old hardware for free from work, this was an old Pentium 133Mhz with 32 Mb RAM and a 2 Gig HD. This configuration was more than sufficient for the way I set it up - except maybe for the small HD. The reason I went with new hardware afterall, was the fact that the mobo I had was simply to big to fit in a nice case, so I got one of those small VIA mobo's. The point is that you can easily use (very) old hardware for a project like this.
First you have to get the additional hardware, this is an IR receiver and an LCD display. The IR receiver I used was IRman from evation.com (a Dutch product, yay!), there are, however, several ways of cooking one up yourself.
The LCD I used was a standard 20x4 display with a Hitachi HD44780 chip, this I got from a local electronic parts store. I guess you can get these anywhere on the web. There are several other possibilities for the display, take a look at the
LCDproc hardware page. The HD44780 display comes without wiring so you'll have to fix that up yourself, which may be a bit tricky, especially since these are rather sensitive devices. I've read in a thread on this forum that the displays from MatrixOrbital come all wired up when you buy them.
A guide for wiring a HD44780 LCD can be found
here.
After having sorted out the hardware I installed Slack, and installed it as the very bare minimum. Recompiled the kernel to make it nice and compact and only compile the modules for my specific hardware. I don't remember exactly what components of the system I kept, but it's very little.
The software that runs on it are mpg123, which comes with Slack,
lirc (for the IR),
lcdproc (for the LCD) and
irmp3 to bind it all together. Installing those is pretty straightforward and there are pretty good docs on the respective sites of those packages. Simply compile them on your own box and copy them over to your MP3 box.
Getting your remote control to work can be a pain, but lirc comes with some handy tools to make the process less painful. The best thing is to buy a remote control that lirc already has a config file for.
Well, that's pretty much it. Getting the software installed isn't hard, the only thing that was a real pain was getting the LCD wired. Also stripping the Slack install took some trial and error in seeing how much I could drop while keeping a working system. I have gained a much better understanding of Slackware through this process, however.
It's a fun project to undertake, if you run into any trouble you can always give a shout on this forum.
Good luck!