Re: aluminum trim pieces restoring tricks
The biggest cost with restoring aluminum trim is in the preparation. Aside from cleaning the parts and stripping the anodized finish off, it comes down to straightening and polishing the metal. The brightdip (if desired) and anodizing processes aren't as costly as these steps.
So if you were to bring in nice clean straight parts to a trim shop, the cost will be a lot lower than not.
Another consideration is whether you intend to get your parts "brightdipped". This is the additional process the factories used that gives you that chrome-looking finish. There's a difference between just getting parts anodized and brightdipped+anodized. Brightdipped parts will have a brilliant shine, like chrome, whereas anodized look nice but are more cloudy.
Still aluminum can be polished to look quite nice. The trick is keeping it that way, which is why the factory went with brightdipping (lasts a long time). As DSTARK alluded, you want to seal these aluminum parts once polished. Otherwise oxidation takes place and it will begin corroding. The factory seals with anodizing. Folks with those big aluminum windstream camper trailers swear by Sharkhide. Other folks say Permalac.
The challenge with aluminum is that it has weak adhesion properties. If clearcoat + UV protection is being applied, adhesion promoter with catalyst should also be added to help increase adhesion and long term durability.
Everything comes down to money, time and what you want. In my case, I didn't want to be in the "aluminum maintenance" business where I'm cleaning and polishing aluminum a few times every year. It's not a big deal, and I'm not "above" that kind of work. I just didn't want to deal with it. At the same time, I didn't have an endless budget. So as mentioned above, I found good straight relatively scratch-free parts which I thoroughly cleaned, then brought them to the trim shop for polishing, brightdipping and anodizing.
It cost me more, but I helped save $$ by having good clean parts to start with (which didn't require much prep). The brightdip was a cost-adder, but the incremental hit wasn't a ton actually. In the end, the extra $$ was worth it to me given the trim looks almost like chrome and I don't have to worry about maintenance.
Either way good luck!!