When this website says "First Fork Road #622 - OPEN", that's when you can do just the first box (really the last box if you're floating) alone. Otherwise, you gotta' take it from the top. It's a beaut, so go do it. Post if you see any wood or other hazards, too.
Also, the gauge is WAY downstream, so early in the season it will be a lot lower at the 1st put-in than what the gauge reads. My totally off-the-cuff guess would be like 50% for early season all the way up to 90% in late-June as the season winds down.
At lower levels I'd plan on a long day on the river. Low in my mind
would be less than 7-800 real cfs -- so the gauge might read 1,400 this early in early season.