Coolant System Flush possible? and A/C System rechange/convert?

[vissjb]

I wanted to get my coolant system flushed (as opposed to draining the radiator and refilling), but I've called a few places and the coolant that they use in the flush is not safe for the aluminum system in my MB 380 SE (1985 with 126K miles). Has anybody found a place that can do a flush, or am I stuck just draining and refilling?

Also, my A/C system just doesn't cool like it used to. I checked into getting a recharge, but my 85 uses R12 coolant, which is $60.00 a pound. Is it worth it to convert over to R134 coolant? Anybody know how much coolant it takes? Is this something I can do myself? As somewhat of a side note, do W126's have a cabin air filter? I'm wonder if I just replace that that I might get better air flow.