If you're gonna be doing a lot of gravel riding or trails I would suggest a rigid fork for the rockhopper, or if you'd want to really load up with a lot of touring and camping supplies. A basic chain and cassette shouldn't run you too much money if it's 7 speed, they are pretty cheap these days. The crank shouldn't need to be replaced unless the teeth are pointy. An acera front derailleur would probably work with your crankset. Since you live in Boston and probably have a couple of options for bike co-ops or even used parts on craigslist you could probably snag a good used MTB fork and might even find some other deals on parts.

If you'd be more interested in lighter, faster touring I would consider buying a compact crank(50/35) or even a cyclocross (46/36) crank for your roadbike and get a framebag setup or one of the seatpost racks. I think mavic open pro are pretty solid rims, I'm a big guy and I've been riding them for 5000km without any problems. There's a lot of posts in this forum about people that do lightweight touring, so check out some of the different configurations people run to see if they appeal to what you think you might wanna do. Either bike you have could work for a week-long trip, just depends on what kind of riding you see yourself more likely to do.

Either way I would check out some of the Boston community bike shops so you can save on labour costs and learn anything you might wanna know about your bike if you don't know already.