Here's what I did to replace (most) of the coolant on an MT. I'd say I got at least 1.5 gallons out. I put pure distilled water in, and after running the bleed procedure twice, checked the coolant and it was still slightly blue. I'm guessing the mix is in the 70-80% water range.
I pulled the hose from the water pump. Really easy to access, took about 45 minutes from removing the belly pan to putting it back on.
Location for reference. The power steering lines are just sitting along there for seemingly no reason (it runs in a big U), and I disconnected them from the mount to get access:
View of the hose I removed - has a simple hose clamp on it.
While I had the system out, I replaced the plastic bleed screw with the brass one. Learned from my E36 that these can break anytime.