Thanks for all the advice and support. Last night me and two beefy friends manuvered my radiators in place and I reinstalled them, using teflon tape on the male threads, followed by a little plumbers putty (is that the same as "pipe dope?"). We bled the air and fired up the boiler, now the place is toasty warm, just in time for winter!
My one pucker-inducing moment was with the spud wrench getting the old value out. The ears on the inside of the valve broke off. I cut the nut off then applied heat and a pipe wrench. The piece bent badly but didn't break, and it finally eased out, letting me install the new valve.