G5 Wont Start Up - Maybe Kernel Panic Related

Question

Last evening, my G5 went into sleep mode, but instead of properly doing so, it did the "wind tunnel" effect and wouldn't respond at all, so I had to hard shut down.
I left it overnight and just tried switching on now to try to find out what happened and how to resolve it. No go. I get a quick flash of grey screen, then blank, then back to grey screen, this time with a folder icon with a flashing finder icon in the middle alternating with a question mark.
I think the wind tunnel thing was a sign of a kernel panic, so am reluctant to try resetting PRAM and wiping out any logs. I tried Safe mode boot (hold shift down after chime, right?) and got nothing. Had to hard shut down again as the fans started getting increasingly noisy and I was worried about another kernel panic possibly happening.
I'm not overly tech- or Mac-minded, but not totally dumb, but have tried to search the site for tips on what to do and am not finding anything which is helping me go through this logically, step-by-step to figure out and (hopefully, hopefully, hopefully) resolve the problem, so I need some help on this. Will gladly search out how to perform tasks if need be, just don't know how to analyse/diagnose the problem well.
I installed new RAM (Crucial) a few months back, but I don't think that is the cause of the initial panic. I had peripherals on at the time, so unplugged all USB/other externals except screen and keyboard (both now plugged direct to G5) when trying it just now, but no go. I set up Airport recently with a Netgear router - this might be part/all of the cause? The internet connection was very slow prior to this problem, low signal despite it being about 3-4 metres from router and the only computer online at the time.
Could it be battery failure? I've had the G5 since 2003-04 and haven't changed the battery previously.
Any help on how to proceed with this would be hugely appreciated. Many thanks for rading and posting guys.

Answer 1

Thanks, just printed out that page and will go through it.
I tried using the Tiger OS Install DVD to run Disk Utility. When I use the DVD, the Startup Disk section shows the Install DVD and "Network Startup" (I'm assuming a ref. to my HDrive) which is just an icon with a question mark on it.
Disk Utility and System Profiler (again, using the Install DVD) don't recognise my hard drive at all.
I removed the airport card, too. Experienced one kernel panic (full warning screen came up as I stated the comp, had to shut down and restart) straight after, confirming my suspicions that is the cause of the panics, but no panics thereafter. Still no recognition of HD and still getting the 'missing system folder icon' thing on startup.
Keyboard's operating/recognised, it just isn't effective, since the HD is absent.
Is it possible that the error caused by the airport card could have killed my HD? Obv, I'm really hoping not, and I'm not sure how it could, but would like to know just how screwed I am here.
I'm thinking of trying resetting the PRAM - am I right in thinking the kernel panic logs are less important to me now I'm pretty sure Airport is the culprit? And could a PRAM reset 'save' my HD (i.e. get the computer to recognise it again)? Or is that not possible?
Sorry for the mass of questions, I'll read through the link now.
Will probs order a new battery once this gets sorted anyways, as I'm sure that'll give out at some point in the next 12 months.