I have a 2007 Chevy Trailblazer. This weekend I lost my running lights or low beams. Could it be that both bulbs blew out or could it be a blown fuse? How do I change the bulbs or fuse?

humm.not the parking lighys?? well check the fuses...could be a light switch/dimmer switch/turn sigal switch/bad grounds/bad bulbs... watch this to get you started > www.youtube.com/watch? v=OMYHemqSQyQ

Old question, new answer... It's most likely the "Headlight Driver Module". GM has a new recall on it May 2017, something like 12 years/150,000 miles. If you have to pay for one, they're available anywhere, maybe $40. It's in the underhood fuse box, one of those relays in there. It's a 3-minute job to replace.