We re-painted ours. The big, blue A I R S T R E A M sign is easy, mask off the silver bits with parchment or tape & cut around the raised letter with a x-acto knife, then spray it with Krylon Royal Blue. Peel of the mask and you're done. (Sorry, can't find a picture right now...)
The smaller sign you show is more of an anodized finish and printed (w/o the raised letters) - so that one isn't as easy. If it's in good, but faded shape I would keep that one (we did on our '64 GlobeTrotter). If it's too far gone - get a new one. I belive they are painted/printed so they look pretty different from the originals. If you do get a new one, keep the old one no matter what shape it's in - you can always go back to it & your trailer's 'next owner' may want it.
On our '56 Safari, I painted the small tags with raised letters and removed the paint from the raised portions
Good luck in whatever you decide to do!