Re decals....on our ROO we replaced the rear one. Cost including shipping from FR was about $50. Removal of the old one was a piece of cake. A hair dryer and some time and you're done. Putting the new one on is not hard, but a bit nerve-wracking. I called FR because the instructions were vague to say the least. DH remembered that when we put the name decal on our big boat, the instructions were very good and said to make a solution of Dawn and water, wet the area thoroughly, apply the decal and the soapy water gives you a medium to allow movement to get it lined up. I asked the FR guy and he said all you had to do was press it on....easy for them to say, they do a zillion a day. We did the Dawn and water thing, got a small plastic wallpaper smoothing tool and we had it lined perfectly. Gently smooth out, let it dry and you're good.
Hadn't considered a marine polish, but makes good sense. Boats take a real beating and this may work and hold up better. Again, would suggest the 303 for over your decals. The directions say to repeat every 3 weeks....not likely to happen around here, but it's just a matter of wipe it on, wipe it off. Many swear by the stuff. Guess I'd know for sure if I'd gotten to use it.
BTW, nice looking trailer. Make lots of happy memories.