[G4] OSX questions

[SLarsonIH at aol.com]

I have finally decided to dive head first into OSX. (10.3.9) So, now I have a 
few questions. I am slightly sight impaired so I am looking for answers to my 
questions about OSX and OSX programs either by e-mail/MacLists or web sites. 
So, here goes...

How do I change my administrators password?
What is 'Log Out'?
What are the advantages/disadvantages of having different accounts/users?
When I have iChat active and the screensaver is running, people 'IM' me but I 
don't know it because the screensaver keeps running. Is there a setting I'm 
missing?
I can't find a way to have the cache empty when quitting automatically, 
either with Safari or Firefox or have a Ram Disk for the caches. Is there a browser 
that will do this, or a setting in either browser? Which browser do you guys 
prefer?

I think that's enough for now.
Thanks in advance.
STeve