OOOoo - Yes! There's a great little book called "Birding Portland and
Multnomah County" by John Fitchen, published by Catalyst Publications in Portland.
Powells Bookstore in Portland has it and will probably be willing to ship it.
(Powells itself is another great place to visit.) Also, the book's author, I
think, is a member of the local Audubon Society and he might be able to hook
you up with a guide or take you himself. There must be a website for Audubon
with a "contact us" link.
I'd definitely recommend a full day on Sauvie Island.
Have a great time! I birded in the area a few years ago and am definitely
going back. (If you've got oodles of time, drive east through the Cascades to
Bend and then south to Malheur Refuge - truly awesome birding. However,
there's enough right in Portland to make you very happy.)