As I said, there are lots of options. I want to say I've even read about one guy that claimed he used simple a large cardboard box, like an appliance box, with a light bulb in it...and said it did the trick. Obviously, you do want do make sure you don't create a fire hazard.
Here's another option that I found with a quick Google search, I can't vouch for it, I barely skimmed the article and peaked at the plans, but something like this may be the answer for your basement.Home made Honey Heater!
As to preventing crystallization. I assume you strained your honey when you extracted it...correct? If not, I would certainly suggest it to reduce impurities. I use the coarse pail filter from Kelley Bees, it's 600 microns. You really can't control what the bees forage on. So , the only thing that really leaves in what temperature you store it at.
As too the how long. Depending on the method used, doing it right and not overheating it, I would guess a day or two for a five gallon bucket from what I've heard, but I have no first hand experience.
Keep us posted on the adventure. :)