Reliable local mechanic quotes $800+ to replace head gasket to stop leak. 95 e320 has 101k mi. Since he's going in, he suggests replacing 'looms' because they deteriorate and get brittle with time. If not and looms are damaged during repair, car may come back with rough idle, etc. Doesn't make mechanic look good because problem comes right after new gasket work. Quote is another $600+.

What are looms? Are price quotes reasonable?

Thanks.
KG