What seems to be the overall problem?
There are a couple of bushings that create squeaks, Sway bar for example.
Can you be specific as to what your trying to cure

The problem is with my C230 with 212K miles. I can feel every pebble in the road, and it's very loud too. I feels and sounds like a go kart with no suspension. Lots of road noise transmitted throughout the entire car and bad, severe ride. Ideas, anyone?

I guess you can start with springs and shocks, and I actually changed tires to get a quieter ride, but that's not cheap. Also, ball joints are sometimes a problem. Squeaks over bumps, and braking. Inexpensive fix. Other bushings can be found on Ebay in kits or individual, but the sway bar bushings I had to search the general web to get them.
Get the car up on a hoist and do a full inspection with a pro. That should zero in on the potential parts required.

From a DIY perspective, life will be easier replacing the entire control arm assemblies. If it were my vehicle, I'd do front uppers and lower arms, lower ball joints, shocks absorbers, and sway bar bushings. In the rear I'd do the full five link and shocks.

--Kyle

I agree, with complete arms it's just a unbolt, replace and bolt on scenario. The only problem I see is that the lower arms front and rear are very pricey. It looks significantly less expensive to do just the bushings in the front and rear lowers, and then replace everything else as assemblies. Has anyone ever replaced the bushings in the front and rear lowers? Is it hard to do?

Also, I have a shot rear wheel bearing. Can't seem to find a how to video or tutorial on line. Can anyone point me to one?

Thanks!

Pelican did a fantastic article on the SLK230. Use that one as a reference as the procedure will be the same on your C230

--Kyle