Old 07-08 iMac Update?

My friend recently gave me an old 07-08 iMac that wasn't being used anymore. Now I'm not super tech-savvy, but I've updated the software as far as it will let me which is 10.6.8. I'm just curious if there's a way to physically open up the computer and install newer software/hardware/system that will make it run as if it's relatively new, with modern software. The monitor works beautifully, it's just a shame that it can't update to anything newer or download pretty much anything that now requires higher than 10.6.8.