I have a 1985 DL and today noticed on the tail lights that the bottom outside (red colored lens below the orange one) lens is badly cracked and faded on both sides. In fact the one on the drivers side has a piece missing so it is time to replace them I figure. It's a shame because all of the other lenses are in great shape; no discoloration or cracking.

1. Can I replace just the section that is bad or must I replace the whole unit?

2. Where is the most reasonable place to purchase new or used parts?

Thanks in advance!