Questions on lowered vs stock suspension 2008 m3

Just thought I'd throw this out there.
I'm the proud owner of a few BMWs , a 2012 X5D , a 2009 128iC (soon to be for sale) and my latest a 2008 M3 convertible. I bought the M3 on a deal that I felt was too good to pass up... 2008 with 39,000 miles for $39,000. This car is in amazing shape and appears to have been treated very well by the prior owner. I'm in love with this car and can't wait for dry days to drive it. The few days I've been able to take it on long drives have have been Exhilarating Experiences. I can't find any faults with this M3- the double clutch tranny is an amazing invention. Anyhow, the. M3 has an upgraded exhaust and an upgraded lowered suspension. I'm considering going back to a stock suspension as I fear damaging my front air dam on any steep inclines such as my parking garage at work or my driveway. It does scrape a tiny bit at both of these places if I'm not paying attention and I'd rather not have the worry. The car is not obnoxiously low, and I guess it's been lowered about 1.5".
So I guess I'm asking if anybody knows what's involved in switching back to stock, labor cost, parts, etc. I have no intention of having it done at a BMW dealer unless I'm advised otherwise. I would prefer to use a recommended independent , some names which I've read on this forum. If anybody with a stock M3 is interested in swapping suspensions I'm game for that as well. I just have no idea what's involved. I'm a car guy as far as I love to drive fast and windy roads but I don't know much about the mechanics of these fine automobiles. Any help or advice would be greatly appreciated. I live in Bergen County NJ and have my other 2 cars serviced at Prestige (have nothing to say but great things about them). I just don't want to use them for my M3 as it is out of warranty and I know there are less expensive options to service it.

Stewart