Mercedes Benz 1991 300SL-Help with coolant flush and thermostat replacement

[ytech]

Hey all,
After a long time of searching the forum with no luck, I had to post a new thread as I need some help to preform a coolant flush to my 91' 300SL-24.
I would like to change the coolant since I do not know how old is it and summer can get quite hot here now days.
in addition to the coolant flush , I would also like to change the thermostat, the thermostat housing and the pressure cap of course.
How should I start with the flush? , at what phase of the coolant change should I change the thermostat?. What type of coolant should I use? , how much coolant should I use the refill the system? Finally, How should I bleed the system? I noticed a bleeder cap on the thermostat housing.

Thank You