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Why don't you try to hike something like 12kft first with a rise of 5k feet in a day first then decide?
Odds are you might get yourself killed on this one.
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Odds are good that James won't get himself killed on Kilimanjaro. The majority of the mountain is walkable, and it's not nearly as technical of a climb as many other peaks of similar height. It's considered the worlds highest "walkable" mountain.
James,
I haven't done a ton of mountaineering, especially on higher peaks, but I would recommend getting some basic mountaineering experience and determining how you feel about the sport first. Learn the basics, roping up, crampon techniques, crevasse rescue, etc. You can learn most of these on a lot of technically moderate-to-difficult climbs that can get you a taste of what you'd be in for when climbing a more difficult route like Denali.
I would personally recommend something like
a seven-day training course on Mt. Rainier (14,410ft), which will certainly test your abilities while helping train you for something like Denali or other climbs.
Keep in mind the differences between Denali and a climb like Kilimanjaro are very very large.
Rob