If you shoot me a IM with your Email address I can send you the FSM PDF for changing the water pump, should be in there.
Yes that is an O-ring seal. Look through any timing belt DIY or the FSM that are available and it will show you where and how to change it. Its been a while since I did my belt, and my memory is a little fuzzy lol
Hmm it has 115K on it and I did the timing belt and water pump at the 90k service? Could something have been missed?
I would say yes, or they rolled the O-ring while installing it. If you had the dealer do the belt and pump I would take it back. It defiantly should not be leaking with 25k on it. Sent that PDF.