Its easier to run homebrew with the original PSP so you're actually in luck. I have the original and the entire process took about 10 minutes.
Head over to the psp forums section at afterdawn.com, theres a ton of good information and whatever you can't find people will be quick to help out. Its been so long since I installed my firmware that I wouldn't feel comfortable trying to tell you the process, lest your PSP get bricked somehow.
Homebrew certainly isn't anything super magical, and there are quite a few snes/sega games that run like **** on the PSP, but theres also many that run great. Its a trial and error thing. Some people may get *****y about this, but since PSP games are almost never avaliable for rent anywhere, I download the games and demos to preview them before I make a decision on buying one. I find it very useful. Theres actually alot that can be done with the system through customization and tweaks.
You may need to upgrade your custom firmware according to how sony upgrades the official firmware. For example, vice city stories would not play on any firmware official or custom that was below 3.25. As games are released, its more and more common for sony to require a certain firmware for them in a vain attempt to stop homebrewers from being able to use their psps on newer titles. Almost all of the time there will be a new custom firmware following an official release, and the upgrade process is quite simple.
Ebay does wonders.
"They're everywhere, the little harlots."
-Martyn