Hi, and welcome:
Q#1: When I buy a used car, if it doesn't have complete records, I flush (or have a tech flush) every fluid in the car. MB fluids are usually best - see the archives for a discussion on red vs green coolant. Brake fluid should be done every 2 years anyway, and trans depending on mileage. I have the Power steering and differential fluids changed as well. Next I have all the suspension/subframe bushings checked out. On these id doesn't hurt to have the rear suspension thrust arms checked especially carefully.
Q#2: I believe your wheels are the 6J15ET49 because I don't see a Sportline badge on the photo of your car, and because my 300E came with 6.5J15ET49 as stock. I don't think they went to the 7" rim on your smaller 190 without the Sportline.
Nice clean car - are you going to put different wheels on it? (Those 15 hole factory wheels are light weight and forged, but a PITA to clean). I installed the 7J15ET36 dished 8 hole polished wheels off of a 1998 C230 - no problems, easier to clean, and looks nice while retaining some of the look of the 8 hole rims MB used on these cars at the last of the model run. (Pics below in my sig line).
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E