Being water cooled does not impact the oil choice. Yes, you can use 15W40 all year, but it wouldn't hurt to switch to 20W50 in the extreme heat.
I found this with a quick Google search:
http://www.motopartsmax.com/index.ph...engine/paID/49
I don't have a clue how many inch-pound the water pump bolts should be. I'd take the cover off, clean it thoroughly, apply new sealant and hand-tighten the bolts.