Hi Ben,
Both the front and the back sections of the reservoir connect to the M.C., but they have different rubber seals.
To remove the res., you have to: unscrew the bolt holding the front part that is accessible through the filler cap, and then pull the rear part of the res. straight up and out of the rubber seal in the M.C. Mine was a tight fit, and I basically just closed my eyes and hoped for the best! Try to squirt some silicone lube in there as you're pulling, and rotate the reservoir at the same time. It did come out without damaging the little reservoir tube that fits inside the rubber seal.
I had ordered a seal kit for my '65, and received part.# 000-586-01-43 (US$11.50), but the rear rubber seal was too small in diameter. The front rubber seal looks like a generic o-ring.
Will W14
1965 230SL 4spd
Victoria,BC