Is there sutch a site where for eg. would describe in photos how to update a macs ram, how to open it ore even replace the HD or CPU? or whatever upgrade one needs to make? has a lot of illustrated tutorials for hard drives and other upgrades.

Replacing RAM, hard drives and CPUs in a Mac is fairly easy -- if you decide to upgrade any of those components, we can walk you through the exact process, and if that doesn't help, we can point you to a specific illustrated document on how to do it.

Might wanna pm bobw. He's got a list of Apple service manuals, which illustrate how to upgrade/replace just about any component on Macintosh computers.
well there are 2 upgrades i want to make on an eMac 900 Mhz
1. upgrade its memory
2. fit in a brand new OS...what else MacOSX, its running 9 right now