Welcome to the site. The part that is dangling can be re-attached with some weatherstrip adhesive. Since you are new, I really recommend trying the search function. It works well and you'll be surprised what you will stumble across while searching. I did a quick search in the DIY section to address your question about restoring the door belt trim. This thread has a couple suggestions. http://www.regalgs.o...er-window-trim/
Everyone on the forum that first installed a downpipe and then later installed headers, raise your hand. I'm willing to guess there are a lot of hands in the air. If cost is about the same, go with headers.