Really, all you have to do is drain the coolant level below the bottom of the lower radiator hose where it meets the thermostat housing. Heh, how do you tell that? I dunno, just drain about a quart or so out.
When you refill, remember to burp the system via the bleed valve which should be located at the front side of the engine near the other radiator hose.
Bogatyr
See, don't you wish you had the shop manual?