Send a PM to ASD. He and Crusty Chief made the trip a couple of years ago and can share a lot of info.
I live on the Columbia just above where the Snake empties into it. I've traveled the rivers from Lewiston down as far as Portland so can help with info on these parts of the rivers, the locks, etc.
By way of a P.S., I have put together an Excel file that has mileages of locks, cities, marinas up and down the Columbia River. It also has a page in the file that contains the radio call signs and phone numbers for the locks, many marinas, fuel companies and other points up and down the river. If you would like a copy, PM me with your email address and I'll send it out to you.
Also, with any other questions, PM me or fire away on here. I've boated here for 40 years and can give you some info if you need it.