Additional tips:
1) Figure out the metro system. It's not too complicated and will get you from your hotel (which looks like it is not too far from the Lepanto stop) across to the Colosseum in a jiffy. Be warned that rush hour can be crowded and watch out for pickpockets. I assume you have seen and plan to follow the money belt warnings.
2) Directions can be confusing. Recommend a compass. We looped an extra 10 minutes away from Piazza Navona because the road didn't go through and we headed the wrong way.
3) I highly recommend Orvieto. We spent 2 days there and it was lovely. Alternatively, Ostia Antica is very neat, especially if you are into ancient Rome. Either makes an excellent day trip out of Rome and I would be hard-pressed to choose.
4) Stop and eat the gelato. Seriously. I know it's winter, but it's gelato and it's Italy. :-)
5) It's winter. It will be chilly. Long underwear, gloves, waterproof shoes all recommended. Scarves can be purchased in Rome. If it will be sunny, bring sunglasses. I nearly went blind the first two days there. Have jackets with hood in case it rains.
6) If it rains, try to get to the Pantheon to see the rain coming down through the hole.
7) Trastevere is very quirky and interesting, and not too far from your hotel. Recommend strolling around there one night and visiting Rick's recommended gelateria.
8) St. Peters' Dome is quite a climb, but if you are fit, the view is spectacular. Being winter, it will get dark earlier so plan your schedule accordingly.
Hmm, that's all I got for now. If you have more questions, post away.