HELP! I need advice on regionalized keyword terms in AW....

[tclcorp]

Am new here so HI everybody! I own a small local service co. We serve about 25 mi. radius from our office. I've had 2 AW campaigns for 8 mos. with good results. 1st camp. is local, 2nd is regional (no desire to run national). Both have nearly identical keywords, ad-copy and ad-groups. Both campaigns use ONLY "expanded" and [exact] keywords, no broad. I'm thinking of focusing on target market even further by adding regional terms, i.e., city, town, zip code, etc... I asked this ? in another forum and got 1 good answer that made sense. But, anywhere else, I get no replies. Even on the "official" Google HELP forum I have yet to get a reply after 3 days. I'm just looking for a 2nd opinion before I go thru and do all the work, or worse, screw up my campaigns which have worked well the way they are. Here's my questions:
1. Do I even need to narrow the keywords down with regional terms since our ads are already showing in our service area, ONLY?
2. If you suggest I add regional keywords, which campaign should I add them to - local, regional or both? And, if I add these "new and improved" regionalized keywords, do I then remove the old keywords/phrases that have worked well since the start? Afterall, they would still be covered in the remaining campaign still.
3. If I should add these new regionalized keywords, how should I set it up? I assume taking an "old" keyword and adding the city or zip code or town, etc.. first in front of the old keyword, then make another "new and improved" keyword with the city, town, etc... behind it. But, what about best phrase? I assume I would use only "expanded" and [exact], right?
4. Would I need to change my ad-copy at all to include the new terms in it? We worked hard creating relatively successful campaigns (3.1% and 3.8% CTR with a good ROI)and these ads seem to be working well, I'd HATE to lose my position, CTR, Quality Score, etc...just for adding or deleting words/ad-copy.
5. Finally, could I just add the city or zip code, etc... as newly introduced keywords to my existing campaigns? As Broad phrase, of course.

Sorry this is soooo long, but I wanted to make my ?'s clear. Hopefully, I can get some further advice on this from you folks in here. Thanks in advance. Mark