Do a search by my name. I also own an 89 560SEL, and have done lots of work on it. Besides the timing chain and rails, (very important), and the self leveling rear accumulators, I did the reaction ball joints in the front end, (failure is indicated by a "klunk" while braking), front rotors and pads, rear sway bar links, (other klunk noise, inside rear wheel), steering shock, all tie rod ends, replaced idler arm bushings, and intend to re seal the steering box sometime real soon. Another thing to check is the dome light. If it does not come on with the driver's door, but does with passenger door, there may be troubles with the relay controlling the alarm and light. Usually problems on the PC board in the relay. Check the idle speed. 550 rpm in park when warm. Anything higher is trouble in the idle control circuit someplace.
I think I have about $2000 in parts over the past couple of years, and 20,000 miles, since I bought mine, (with 125K on it then.) This cost includes flushing and replacing all fluids, a new battery, everything above I listed, a CD changer, bubble over the sunroof, hood pad insulation, and a handfull of other things I am sure I forgot. I do all my own labor, (sucker for punishment), as that is my idea of a good time. I have a florida car too, so no rust issues exist here.
I posted questions on most of these items, so really take a look. Parts are not too expensive, really, if you can order them in advance off the board here. Walk into a dealership and prepare to get robbed!
Gas is also expensive. Expect under 15 mpg in traffic, around 20 highway. But it is the best car on the road, IMHO. I love mine.
Good luck, and have fun!
1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)