PowerPC :: G4 Not Booting - Hold Power Button And Restart Computer

Got a tricky one here: powerbook G4, 1.25ghz, 1GB RAM (2x512), 80gb HD, APX, 15" LCD, serviceable battery, SuperDrive, OS: 10.4.11. It was brought to me with a boot problem: Computer turns on, gives the start up sound, backlight comes on, apple logo shows, spinner spins... then you get the dimmed screen, large option icon and "You must hold the power button and restart your computer": a kernel panic. I've seen this a few times before and the last time, I fixed it with a new hard drive and the removal of RAM from a bad ram slot.

What I did was:
1) Replaced existing 80GB HD with a backup 30GB drive. Then booted with a Tiger CD (the computer won't start with my disk warrior cd, nor with a tiger DVD). I was able to install Tiger and restart the computer. But the airport card doesn't show up. I tried a known good airport extreme card and this too has not shown up.
2) I hooked up the 80GB drive to my PC via MacDisk and checked it. Sure 'nuf it had loads of problems. MacDisk went through and fixed it (I'm not sure what the problems were as I'm new to MacDisk and don't know what it's looking for and fixing when it does).
3) With the computer running the 30GB known good HD, I started having the same kernel panics so I removed the first RAM chip (512MB) and tried to reset the PRAM.... here's where it went wonky. (I know, only change one thing at a time...)
4) As I said I tried to reset the PRAM (Option, Command, P, R, at start up). While I can get the computer to not boot, it won't restart. I don't know if this is just unique to this machine. Next I tried to reset the NVRAM and again got nothing. The screen wouldn't come on at all. After about three or four resets, the computer did start in Open Firmware mode. I reset the NVRAM from there and restarted (reset-nvram, reset-all). Still nothing on restart.
5) After trying to start it 15 times like this, I swapped the bottom RAM card to the top slot and removed the airport card (again, I'm stupidly trying to change two things at a time). BAM, computer boots... I put back in the 80GB drive that's been "fixed" by MacDrive and BAM, that boots fine too.

So then I put back in the airport card and it will boot, but won't recognize the airport card. I've re-seated it about a dozen times and have used terminal cleaner on the card and on the socket for the ribbon cable from the card slot to the logic board. As it sits, I can't get the airport card (either of the two) to show up at all. I did realize that the open firmware did reference a problem, but I forget the code now and when I looked it up, the references were to a failure of the airport card, but there were also more general references, so I can't be sure.

I'm thinking now that it's the airport card controller on the logic board, the bottom RAM slot and a corruption of the hard drive. Yes, there was a history of moisture into the device and I think a drop in it's past too. I'm the Mac repair technician for the people at the local bike shop, so I get to trade my repair work for their bike repair work. The problem is that they ride their laptops like their bikes, hard and greasy. I'm really wondering about ways to get the airport card back up and running. Or, baring that, a good card-based wireless adapter that I can slide in.