Hi,
I had the 300D and succesfully installed the hack on it quite a few years ago. I don't think that many people had problems with the installation back then, and if it were me, I'd do it again. I think the site I downloaded the hack from had fairly comprehensive instructions, and from what I remember it was pretty easy.
It gave you quite a few things, but most important to me, were mirror lockup, flash compensation, allowing selection of raw+small jpeg, and ISO 3200.
The 300D is a great camera and I still use mine from time to time and it's perfect for your first digi SLR. It was far superior to any of the film SLR cameras I've had in the past. The images it produces can still hold their own, in fact I have two A3 prints in an exhibition right now that were taken on the 300D. The only thing that bugged me was the amount of noise that can creep in, and the small buffer size if you are doing anything like motorsport - not huge problems though.
Have fun with it.
Mark.