My car has been acting up ever since it has gotten cold out. It doesn't want to stay started in the mornings. My headlights get brighter when i give it some gas. Does this have something to do with the alternator? There are also odd noises here and there. Also how hard is it to change u-joints? Should I just change the back since they are bad or should I change the front too? I will be doing this in a couple days so im just getting prepared awhile. Thanks ahead of time for any responses.