You really should take a Scuba Refresher Course, before diving back into open water.
You're fortunate.
You have over half-dozen dive shops in Portland.
Call first and see who offers the class, and then go down and visit with them.
Check out the shop and vibes you get from staff. Look at what gear they sell. Take a list of questions with you. Ask how they blend their Nitrox.
Before you buy internet, ask the LDS to match prices. Mine does (or beats).
Some dive shops are actually cool to hang out at.