g5 ram question and hard drive

I just got a daul 2.3 g5. it has 2.5 gb of ram and 250gb hard drive I want to put more ram in it and another hard drive What kind of ram can i use can i buy some off of newegg that is something like g.skill and does it take ddr or ddr 2? and could it damage the computer? lastly can i put a 500gb hard drive into it and what kind do i need ide or sata?
thanks

you should find RAM that is labelled as being compatible with a g5 mac, you can get it on the well know auction site 'flea'-bay (dunno if you're allowed to post the real name) as for the hard drive you can use a standard SATA hard drive, i just installed a 1TB one in my dual 2.5 so i'm sure 500GB will be ok