I don't think the noise I am hearing will cause any damage if you drive it as long as the oil pressure is good. I'd get another filter and try it. You don't have to change the oil, just the filter. If I am going to replace just the filter, how much ...
I bought touch up paint last week, so I might try that the next hot day. And, I try to stay away from dealerships as much as possible, since my exhaust ruined my extended warranty and all, plus the hassle.
I'd rather see beat-to-shit paint than mud flaps on my truck. You could touch up the big chip. Of the fine scratches aren't too deep get some red vinyl to cover it, similar to the OEM stuff the put on the bedsides.
Too much heat under the hood, chance of water damage if mounting under the truck. I put mine behind the rear seat in my 04 crew cab. Routed the airlines though the cab vents worked awesome