Will be installing new hard drive on G4, know the mechanics, but concerned about partitioning and formating...anything special needed other than my install cd that came with computer? If I can get the old hd to start one more time, should I put new in as slave, format it and then copy info from old drive to new, and then change positions? Am I on the right track?

Yes, but:

The transfer of OS, Apps, extensions, and
such are something that may not transfer
intact or in thier entirety from a faulty drive.
And for these things, which you already
have installer disks for, there is no
reason not to clean install all of them.
As far as data goes, well..., I would mount
the new HD as master, the OLD HD as
slave. Transfer the data. Then remove the
old drive and throw it away so as not to be
tempted to rely on it 'just one more time'.
I mean if it works sort of OK, then leave it
there and only use it for temporary
bullsh*t storage or a place to keep a load
of FONTS on board or something like
that. Dispensible items is what I am
referring to. If you lose them...OH WELL.

When installing the new drive I would
partiton it. If you use Photoshop or
another image or video editing app which
relies on scratch space be sure to make
a separate partition (or 2 or 3) for that.
Use a folder on the scratch partition for
the CACHE of ANY app using cache as
well. Idea is that you can erase and clean
out the scratch partition independently
from the OS & Apps, and the
fragmentation on the scratch partition will
not invade the OS & Apps & such.

My opinions.........