They're raising the bridge by about 60 feet at its center. Long story short, they're building a second level above the first, and will then start removing the lower level. It's a multi-year project.
Auto traffic will be limited to single lanes for at least some of the construction. There will almost certainly be some night & weekend closures.
As far as I know, they aren't eliminating the walkways.
I recommend you check with Transportation Alternatives. They may have a pretty good idea of what's going on, and they have a depth of experience and the machinery for bicycle-related advocacy.