Hey y'all... thanks for the responses. There's a community bike shop in this town that's open Sundays and Wednesdays (but not today) where I've been putting in a dozen hours or so a week. It's pretty disorganized, but there are mountains (literally) of virtually every type of component you can imagine. I guess I'm just going to see what fits this Sunday.. I'll keep in mind that markings are more or less meaningless! There isn't much clearance left (~6mm to frame), I'll probably end up just keeping the 28 on the back and getting a better front tire, probably a 25 or a 28. Depends a lot on what's available in the mountain in good condition.
Also:
not sure why you need to go 32s in the rear, 28s are already pretty meaty on a road bike
because I'm coming off a hybridized mountain bike and have BMXer experience/lifestyle, so it's a little hard for me to resist jumping up curbs/flying off them. Not tryin'a eat pavement though, so I've resisted. I'd just like something a little meatier/lower PSI/that's not gonna pop if I'm bunny hopping. I know the response to this is "that's not the right bike for what you're doing, then."
Are you going to put fenders on it for commuting in bad weather? That could reduce the clearance.
Nah, but good thing to consider, thanks for mentioning!