I never thought I'd be the one to be saying it, but get a scanner
9600 systems are a lot more complicated to program correctly for monitoring only. A good overview was written up by ElroyJetson
here. If it isn't done right, you can either not hear anything at all or you affiliate by accident and could put a cop, firefighter, paramedic at real risk because they didn't hear a call or couldn't ask for help. If you've never programmed a 3600 system, I would highly recommend AGAINST trying to dive right into a 9600 system.
With that disclaimer out of the way...
With the "scanner" you're programming, I would put the main CC for the Detroit simulcast as well as the 3 alternates. I flew into DTW a few times for my own buffing trips years ago and put the sites between the airport and the city in my scanner so I wouldn't lose any coverage going back and forth. If you sort the MPSCS system sites by county, they should all be in Wayne county, just compare the sites to a map of your route.
As far as your trip goes, There's a lot of focus on this time of year and there will more than likely be state and federal authorities around the city due to the increase in arson. My biggest piece of advice is to not be on scene before any apparatus. If you see something, drive around the block for a few minutes, you can save yourself some hassle down the road. A lot of the firefighters are laid back and love talking to people who come to town, but that isn't universal. Don't take it as an insult, but some of them are tired of being a national focus for what is such a bad thing.
If there's a lull in the action, there's lots to check out around downtown. There's some abandoned mansions around Edmund & John R. Take a trip over to Belle Isle Park for the shots of the Renaissance building and skyline you always see of Detroit.
Lastly, use your buffing instincts. If you hear one area is starting to get busy, check it out. On my first trip one of my friends stuck around in the 9th battalion and didn't see anything all night, we went over to squad 6 and followed them all night. Prepare to not get back to your hotel until about 6-7 am