I actually have a draft in a few minutes, so I have to be quick. You have a good point about Marmol, but I think you're overestimating how many innings he gets. In most cases, I think he pitches only one inning, same as Gregg. In some cases, he'll pitch 2. I think 3 inning outings will be VERY rare, and I doubt he ever goes 4. Over the course of the season, IF the roles stay intact (Gregg as closer, Marmol as setup/important innings guy -- big if, of course), I imagine he might get 20-30 innings more. I don't think it'll be enough to make up for the saves. One way to check is to compare what he and Wood did last year (Marmol would be in basically the same role, and he had about 20 ip more than Wood). My guess is that Wood was still more valuable, but it's worth checking.
And I'm not saying you have to drop Marmol. I'd be hesitant about doing that. (And certainly at least wait for the closer announcement tomorrow.) But it would at least be good to get another true reliever for the days Reyes isn't pitching.
As for catcher, Navarro is okay, dependable. I'd find a way to stash Wieters, because the payoff for you is pretty great (especially in a h2h, where it's more important to dominate at the end of the season than at the beginning). At least try to pick him up before his call-up, because catcher is a big weak spot for you. As for the others, again, I'd compare what they did last year. And personally, I'd go for Posada (probably -- again, I'd have to check how the points work out). Too much upside, especially when he won't take as much wear and tear, not catching every day. Also, if Sandoval is available and qualifies at catcher, he's a guy I love -- good hitter, and should be the everyday 3b for the Giants. So he'll play more than most catchers and not take quite the beating.