Welcome, I see you are about to make a huge mistake - let's see if we can avoid that.

1) Check engine light - stop by Autozone or some other parts store and get the codes read, report back here and we can help.
BETTER YET, buy your own code reader and read them yourself - it's not hard.

2) The dome lights in the 04 coupe have a three way switch on the over head console.
Position 1 - Lights are on all the time
Position 2 - Lights come on with opening of door (and I think hatch)
Position 3 - Lights do not come on ever
Check all three positions, if you cant get them to come on, check fuse 9 in the underhood fuse box, driver's side.

3) Loose molding - I will let a coupe owner handle that one, I've never owned a coupe.

4) THe key fob can loose sync with the SKREEM. Follow the programming procedure:
A) Get in car, insert key but do not turn it.
B) Press unlock or lock button on key twice.
C) Turn key to ON but don't start car, within 10 seconds.
D) Yank key out and get outta car, close door, try buttons, they should work.
E) If the above does not work, replace batteries in the key fob, repeat procedure.

Now to your mistake:
If you take the car to any 'oil change' chain, plan on big trouble. (In fact, if you take your Ford pickup to one of them, assume things won't get done right, either).
Oil changes are easy to do on your own, I'd do it at home myself. If you don't want to do that, find some small garage known for Mercedes experience and take it to them. They will know to use a FLeece Filter and will have oils in stock suitable; additionally, you will develop a relationship with people who know German cars, and you will need them someday. Also, they will know about the o-rings that Jiffy Lube will just throw away, instead of changing them.

Walmart sells 0W40 Mobile 1, but I'd not use it south of, about, the Canadian border. The current recommendation is, and has been, for at least five years to use 5W40.
Here is the list of approved oils, 0W40 is still approved but no longer recommended:
https://bevo.mercedes-benz.com/bevolisten/229.3_en.html

DO NOT use a paper oil filter, you want a "Fleece" filter, here are two re-boxed Mann Fleece filters you can buy locally:


Here are two filters, the white one is Fleece, brown one is paper. Verify what is in the box before you take it home.
If you tell the guy behind the counter you have a Crossfire, he will sell you a cheap paper filter, cause the computer tells him to.
If you tell him it's a "2003 Mercedes SLK320" he will sell you a fleece filter - yet the engine is the same engine, built by the same factory, in both cars.


LEFT: FLEECE --------------------- RIGHT: PAPER
The box will have several 0-rings for you to replace on the filter carrier, one o-ring we dont use and throw away, the rest we replace at every change.
Jiffy lube just throws the 0-rings away (in my experience, anyway).