iMac will not boot please help

hello and thank you in advance for any assistance you can provide. i've been trying troubleshoot an early 2008 imac for an elderly couple and haven't been able to get anywhere with one exception...I was able to boot into single user mode once and thats it! I've tried reseting smc and nvram, safe mode, swapping memory etc... and all I get is a grey screen prompting to restart the computer. I thought the firmware might possibly corrupt but unfortunately this particular model doesn't have any EFI downloads factory or updated. One forum I was on had several iMac 8,1 owners with video card related issues but I've not even been able to get far enough to determine if thats the issue. The couple had the iMac in storage along with whatever original software it came with but unfortunately (6 boxes later) I haven't located anything other than the physical iMac. I come from mostly a windows background though I do run several linux vm's and a little Mac experience starting about 6 months ago when I repaired some physical damage on a mac book pro and fell in love with the hardware +design and wish I'd picked one up sooner.

Anyhow back to the problem, can anyone please give me some direction in getting the iMac to breath once again.

cheers

~OP

Model Name: iMac

Model Identifier: iMac8,1

Processor Name: Intel Core 2 Duo

Processor Speed: 3.06 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache: 6 MB

Memory: 4 GB

Bus Speed: 1.07 GHz

Boot ROM Version: IM81.00C1.B00