Also an aside note, whatever wheels you get that may be different from what came on your car originally, you must make sure they have the right wheel studs/bolts or nuts, whatever to hold them onto the car. There are apparently three different shapes to the part where it meets the hole in the wheel, and that shape must be the right one for the wheels, and then also the length has to be right. Years ago I had a Black 1987 W124 300E and found some very nice wheels on craigslist for a low price, a fellow Benz nut. He brought them over to my house and I bought them. He advised to take them to a tire shop for proper install, and I was glad I did. The guys sent the store manager out, and he took a look and did some measuring and said he would have to order the wheel bolts! I was surprised, thinking I'd drive home that day with the wheels on my car. Three or four days later they called to say the bolts had arrived, and when I got there they showed me the different shapes, and different length of the bolts. The wheels fit perfectly and stayed on the car the rest of the time I owned it. A set of the right wheel bolts can cost as much as $70, if they don't come with the wheels you buy. And that was about 15 years ago.
Ever since then, I have been aware to make sure of using the right bolts, etc for the job.
Ten years ago I bought a 1996 W202 C220 from a guy, it had the dreaded engine wiring harness issue which I fixed, it had beautiful Carlsson wheels on it, which I found out were held on with wrong bolts: Round ball shape where the bolt meets the wheel. It was supposed to have the other shape. Also the bolts were too short, there's a minimum number of threads that are supposed to engage. I had another tire shop order me the right bolts!
When I got my SL550's wheels from Tirerack they included the right bolts to work with the car. So yes, if you're buying wheels from someone else's car, you have to look into the hole, some have a ball shape, some have cone shaped where the bolt contacts in the wheel. They may be the same as the ones you already have, or they may not! And obviously you don't want studs that are too short! Often the seller will have the wheel bolts for the wheels... These cars ain't very slow, and to keep the carbon from building up in the engine it's important to go fast once in a while, and you gotta know your wheels are on right. I also am not a fan of spacers, although if fit properly I guess they can be safe enough, though I will never use them.
If your car has TPMS but your wheels don't have sensors, that will cost a couple hundred bucks to have a tire shop install sensors, depending on where you go. The TPMS can be disabled using star system (SDS), but why would you do that. I like having the car tell me if a tire's pressure is low!! On my S-Class S550, I can dial up the tire pressures and watch them all on the dash as I drive, if I go on a long trip, they'll go from 33PSI up to about 36 at the tires warm up. My SL550 had wheels without sensors when I bought it, so a little orange tire warning light was lit on the dash all the time. One wheel leaked air, so I decided to buy all new wheels and tires with new sensors, and that was two summers ago. Perfect ever since. It's best to have sensors put in when you're buying tires because then they won't charge you labor for putting them in, and they'd only cost around 25-30 bucks each at that point.