It's very rare that a Mac will support an earlier version of OS X - that is, a version that was released prior to the release of the machine in question. The drivers alone would be a pain, you'd probably have to do some crazy stuff with kexts (for some really good info on that kind of deep magic, check out the Hackintosh Support Communitites section of hackintosh.com for links to some smart people and conversations). In any case, it will likely be quite difficult to get it working. However...
If you really want to, you might as well try! Don't worry so much about wiping the drive; since the Mac came with OS X Lion installed (even though it originally didn't), and as long as you have installed all your Software Updates, you can use Lion Recovery to reinstall the entire OS, even to a blank drive (useful in the case of drive failure or replacement/upgrade).
Also, target disk mode would be a good place to start, I'd imagine. Your Mac will actually prevent you from booting from an earlier version's install disc, so you'd have to have a disc with 10.6.6 or later on it. For example, booting from the current Snow Leopard retail disc (10.6.3) won't do it.
Your best bet is probably to see if you can find anyone selling the restore disc that originally came with your model. Try searching eBay/craigslist for your model number and good luck!