Well, you can always run a long cable from the jack to your computer. I used to live in an apartment with the coax jack in one room and my computer in the other, so I got a long coax cable, plugged it into the wall jack, then tucked the length of the cable under the wall molding and traced the length of the wall all the way to my computer. It was just about as good as having the jack and computer in the same room - the only problem was when I went to move and removed the cable, I pulled on it rather indiscriminately and ended up snagging the cable on a carpet tack and tearing it open. But, replacing a $20 cable was a lot better than paying $100 or more to have someone knock holes in my wall to install a new jack.
A wireless network router is another option - you setup the modem at the coax jack, then the modem plugs into the router. The router broadcasts a signal that can be picked up by wireless network recievers (which is probably built into your computer if you have a Mac that's less than five years old.) Maintaining a wireless network is a little complicated though, so if you don't mind tacking some coax around the house - probably along your ceiling, from what I know about your pet situation - it would probably be easier to just go wired.
One thing I wouldn't recommend doing is having Comcast or someone else come in and install a new jack in your computer room. It's fantastically expensive. It's actually something most people could do for themselves with one of those do-it-yourself home maintenance books, but it's kind of a pain the first time you do it.
PS - If you do decide to just use a long cable, it's better to get a long coax cable, as opposed to a long ethernet cable. Ordinary ethernet cables are more prone to electrical interference than coax, so you'll get faster service if the majority of the distance between your computer and your wall jack is bridged by coax. (Or you can buy an expensive shielded ethernet cable, but it's not worth the money if you ask me.) Along the same lines, it's best to use cables that are just as long as you need and not much longer; cables that are coiled over themselves actually interfere with their own signals, due to overlapping of the magenetic field that surrounds the wires when they're carrying electricity. You're paying for that extra speed, so you might as well make use of it.