upgrade main HD on G4

[lamblia]

I have a G4 (400MHz upgraded to 1 GHz) with a 20GB HD with 8GB available. I was looking to upgrade it to 120 GB .
The questions are:
1. do I look for one that can run a 400MHz or 1GHz?
2. how can I make it the main HD?
3. am I asking the right questions for what I want to do?
Thanks

 

[pastrychef]

Any ATA hard drive up to 120GB should work fine. There's no such thing as a hard drive made for 400MHz or 1GHz.

You can make the new hard drive your boot drive by selecting it in Preferences after you install the OS.