10.5.8 upgrades, icloud, mini ipad

Hi,

I have an iMac OS X 10.5.8. It's a 1Ghz PPC G4. It currently has 768MB RAM. I have iTunes 10.6.3. I just bought a mini iPad for my son. Here's where I am at. I want to sync the iPad to the iMac but I'm told I need an upgrade to a newer iTunes. I can't upgrade because of my current OS. Can I upgrade to a newer OS with my current iMac, perhaps by adding RAM?

I also wanted to get some of my stuff onto iCloud which does not seem to be an option with this iMac. It only has Mobile Me which I am not sure would be compatible to iCloud or if I use it can I then access the contents with the iPad. And would I then be able to move the content on Mobile Me into iCloud at a future date with a newer desktop?

Lastly, to anyone who reads this, I have been trying to login to Support. I have my ID and password for my Apple/iTunes account. I log in and my infor comes up and then I am asked for my screen name which I believe is correct butwhatever I put in I get a message that says there's already an account with this user ID. So I couldn't sign in to Communities or get any help. I had to set up a new email and account etc. How do I get passed that screen asking me for a screen name? Shouldn't that be automatic when I login?