The head gasket on a 3.2 liter M104 engine would range from $1,200-$1,600 at an independent (depending on whether or not you did valve guides / seals at the same time), and probably $1,800 - $2,400 at the dealer.
A wiring harness costs about $500, and 2.5- 3.0 hours labor to replace. A dealer would charge more for the harness. You can compare labor rates from those at the dealer to an independent.
Most independents charge $60-$65 / hr., while the dealers charge $90-$100 / hour for labor.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".