Take it back to the place and make them fix the problems that arose when the car was there!
But what to check... hmmm, you've checked all fuses? Replace anyway, there can be hairline cracks in them. They are cheap so I'd replace them all if I were you.
Also, this sounds similar to some problem with my car after the fuse box had been messed with. One of the rows of fuses (of 3 on separate holders in fuse box) was not put back into place all the way, thus I lose a 1/3 of my power components, or everything that was fused in that row. Make sure it's they're all in tight, mine needed to be unscrewed.
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)