Help : adding storage to G5

Hello.I have a G5 Dual 2Ghz 150 Gb of storage and now only 12Gb left. I do a lot of video editing and need at least 500 Gb of added storage. Can I do it myself,meaning is it easy to add internal storage to the G5? The apple store guy says he would like to keep the mac for a a couple of days and that is very inconvenient for me. Thanks for any advice.

I'd get an external HD .... they are coming down in price and I saw a 320GB drive for about $AUS150 .... I also saw a 500GB drive for under $AUS200 ....

Thanks for your advice. That is definitely an option I am considering. But I would also like to have more storage on my G5. Can I do it on my own or should I have to take it to the store?

What do you think of this? it is selling for
310 US $.
LACIE d2 Quadra 1TB 7200 RPM 3.5" USB 2.0 / IEEE 1394a / IEEE 1394b / eSATA External Hard Drive Model 301224U

That looks like a good drive. eSATA, one firewire 400 port and two 800 firewire ports and aluminum casing. $310.00 is nearly $100.00 cheaper than what it's going for on LaCie's site. Are they throwing in the cables as well?

Thanks again.I heard bad stories about Lacie. So I went for the Western digital 1TB. it is awesome.