I had and existing gfci power outlet. I had some remodeling done, and now I want to put a new gfci power outlet in. Does this power come off directly from the breaker panel, or can I use an existing power source?

The GFCI outlet is just like a regular outlet except it trips when it detects current in the ground conductor. You would hook this up to whatever power source you have (assuming you are replacing a regular outlet). It is not a special circuit from the breaker panel.

Hope this helps,
WallyH

There are two kinds, a GFCI that is a breaker inside your fuse box and the kind that is a wall outlet. If you have the wall outlet it will protect all subsequent outlets connected to it on that line, you don't need more than one GFCI outlet on one wire.

There are two kinds, a GFCI that is a breaker inside your fuse box and the kind that is a wall outlet. If you have the wall outlet it will protect all subsequent outlets connected to it on that line, you don't need more than one GFCI outlet on one wire.
Absolutely correct!
I'd go for the outlet version since it is easier/safer to install.

WallyH

If you have the wall outlet it will protect all subsequent outlets connected to it on that line,.....This is only true IF it the circuit is wired that way. You can choose to use either the LINE or the LOAD terminals to continue the circuit from the GFI receptacle.

This is only true IF it the circuit is wired that way. You can choose to use either the LINE or the LOAD terminals to continue the circuit from the GFI receptacle.
Indeed! Using the LOAD terminals will provide GFI protection to the downstream outlets. Using the LINE terminals provides GFI protection only to the GFI outlet itself. Depending on what you need, you can have it either way.

WallyH