Tell him to do it himself, it's his PS3...
Anyhow, the easiest thing to do would be to buy a router. You can get either a wired or wireless router, depending if you want to put an ethernet cable from your modem to your PS3.
But if you still want to use the PC method here's what you need to do:
Desktop: You need 2 ethernet ports on your computer. Plug one cord from your PS3 to your PC. The other port goes from your PC to your internet.
Laptop: You need to run an ad-hoc network from your wireless card, and have your PS3 connect to that network. The easier way would be to connect your PS3 to your laptop via ethernet, and then connect to a wireless internet (either wifi point or broadband card), but if you had a wifi point you should just connect your PS3 to that!
In any case, once your PS3 is linked up to the computer, go into Network Connections, highlight both connections, and select "Bridge." To use your computer's internet again, select unbridge.
I've tried the ad-hoc thing, couldn't get it to work. I am also unsure if you need a "crossover" ethernet cable for the PS3 to PC.
It's easier, and less of a hassle to just buy a router. That way you can get online without having your PC on. If you get a wired one, it'll only be about $20. Don't go for fancy gigabit (you probably can't utilize it with all of your devices). If you get a wifi router, just get a $60 wireless-g router. Don't buy wifi-n.
D-Link and Linksys are good brands.