I bring my '00 300m to a local Chrysler dealer's oil-change bay where I wait for them to change the oil and oil filter.
(While I'm waiting, I'll go into the show room and tell a sales guy that I would buy a Challenger if they came in front-wheel-drive, and I'll also bitch about Chrysler going down-hill when they were acquired by Daimler causing them to drop their plans to build the 300N which was shown at the 2000 Detroit Auto Show and which I would have bought had they made it, but instead I'm still driving my 11-year-old 300m because Chrysler doesn't make a proper near-luxury performance sedan).
They generally will check the tire air pressure, lube the door hinges and refill the windshield washer tank as part of the package. I guess it costs me $35 for all this. They'll run the car through their car wash too before they hand me the keys. I'm probably there for 1/2 hour, depending on how busy it is (they can do 2 cars at the same time).
They always change the small window sticker they put in the upper corner of the windshield showing the next date or milage for the next oil change. I think the change interval is 5k km's (about 3k miles) or 3 months. I usually follow the milage number, which ends up being 2 or 3 months later then the date on the sticker. So my 11-year-old 300m gets about 2 oil changes a year. It's got about 95k miles on it. I think during the last couple of years it's getting the best fuel economy that it's ever had in it's life - usually about 28 mpg on the highway (70 mph) and sometimes 31 mpg. I changed the plugs at around 75k miles.
My 2001 Dodge Ram (5.2L) has about 25k miles on it, and it gets 1 oil change per year (on average, but it's not exactly on a regular basis). Both the truck and 300m are kept in my garage when not being driven (definately both are in the garage over-night every night of the year) so I'm not worried about water condensing in the oil making it acidic or anything like that.