Hey, i also have an 03' 620 and I've gone to Riverside Motorsports for spring services and just last summer had them do my 12k service, chain, sprocket, and rear tire. It's not cheap (that last trip cost me $1700) but they are very quick, and are nice guys. They seem to get parts in fast, if they don't already have them on hand. I really could tell a dramatic difference in the bike after the 12k, the timing was a big improvement, it rode like a whole new bike, not nearly as jumpy and studdery. It made me feel like the service was worth it, even though it was almost half what i paid for the bike initially.
The only other shop I've checked out was greater boston motorsports because of the free pickup and drop-off service (nice) after i dumped my bike in December on a sandy steep turn. They were not as on point when it came to ordering parts, and letting me know that parts were not available, but they have been very quick to respond if i kept pinging them. I ended up ordering a lot of the parts i needed on eBay and other online sites because they couldn't get them through Ducati OEM parts. My bike is still in the shop, so i can't comment on the quality of their work yet. I can't wait to get her back!
Bottom line: I want to learn how to do this stuff myself.