I would say go for the 95/96 C280, probably because I have one. But despite the C being below the E in the line-up, in 1995 it was aways ahead of the E.
If you do go ahead and get a C, then make sure the head gasket has been changed, and check to see if the wiring harness has been replaced, if not, then check the condition of it.
As for maintaining the C, I would say it's fairly easy to do, and I couldn't think of why it would be harder then your 420SEL. I just changed the Power Steering Fluid, and i mean, JUST did it, I just got back from cleaning up! It was pretty easy. As for the oil change, easy too. The filter is in the back behind the engine block in a black plastic cover.
I hope this helps.
BTW ALL, Check out my new pix in the Open Discussion!!
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!)