Do you, or have you done, any mountain biking? Honestly, I haven't looked at hybrids in a decade or two, but I think they still suffer from the flaws of any bike (or piece of equipment) that's has its wheels in two camps.
The reason I ask if you have done any mountain biking, or if you might, is to look into getting a mountain bike and putting slicks on it. I have two sets of wheels, one knobby, one slick (although the knobby set hasn't been on the bike in quite a while) for my (very old) mountain bike. I have a rear rack, and I slap some panniers with my change of clothes and shoes in them, and it works out pretty well. I even gave my road bike to a friend (who then turned it into a really cool commuting bike
), since it was just sitting around collecting dust. Then, if I ever want to do real off-road riding, just switch the wheels.
But, yeah, I second Kaffis' question. What kind of pain are you trying to address? Rough roads (shocks)? Narrow storm sewer grates and broken glass in the gutters (wide tires with a thicker tread)? General pain in the bum (which I wouldn't expect, if you're already used to riding a road bike)? Ah, now I see that the Trek 1000 has an aluminum frame. Is overall stiffness the pain you're wanting to address? Don't know how much you'll be able to address that via equipment, unless you get one of those seat-post shocks (which you can mimic by good riding position and pedaling habits, if you ask me).
I would say if you really just want to modify your Trek, you might be able to find some cyclocross tires that should fit your fork. Bars shouldn't be too much of an issue.
If a mountain bike isn't your thing, how about a touring bike? That's going to be much more forgiving - most likely steel instead of aluminum - and will have a nice triple chainring for pedaling under load, etc. (Which, honestly, is why I gave up my road bike. My knees just couldn't handle it anymore.)
Good luck! If you lived in SoCal, I'd go bike shopping with you. I love going bike shopping.