Did my `98 C230 about 10 months back, engine block drain plug is on the passenger side may be between two freeze plugs - 40mmm round depressions- in the block. center to forward on the block horizontal and about 1/3rd up vertically. No need to pull drain plug all the way out
Have some tubing - my guess is about 12mm inner diameter to stuff over the radiator drain plug to guide fluid into bucket instead of having it drip onto cross-member.
Use only Mercedes Benz radiator fluid and distilled water, I premixed my coolant and water with redline Water Wetter before filling in overflow tank.
When fluid is thought to be refilled run engine with radiator cap off for five or ten minutes to rid of air and then fill to between markings on overflow tank.
If this is the second coolant change no need to worry about flushing, if it is your first coolant change get an opinion from the list on flushing. No need to remove thermostat if not flushing for coolant change.
No bleed hole, radiator cap is high enough for this.