Only thing is I have Mac OSX version 10.4.11. Does that mean I have to install snow leopard first?
Yes. Snow Leopard is required since it includes the Mac App Store, which is required to download Lion.
The first step is to ensure you have adequate backups - goes without saying. Then, I recommend installing Snow Leopard and make sure it works the way you expect. Once you determine everything works to your satisfaction, download Lion but install it on a separate volume - preferably an external hard disk. Lion is a major adjustment for many people. You may want to keep a Snow Leopard for various reasons, among them the fact Lion cannot run programs written exclusively for the PowerPC (PPC) whereas Snow Leopard can. You can elect to boot Lion or SL as you see fit.
Lion System Requirements
- Mac computer with an Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
- 2GB of memory
- OS X v10.6.6 or later (v10.6.8 recommended)
- 7GB of available space
- Some features require an Apple ID; terms apply.
Your computer does not meet the minimum memory needs without adding more memory. You will need to purchase and install Snow Leopard then update it to 10.6.8 in order to purchase and download Lion.
The Snow Leopard DVD is $29.00 at any Apple retailer. Lion is $30.00 from the App Store.
BTW, you do not have a G5 iMac. G5s are PPC, not Intel Macs.