Personally I would rather destroy the bulb ,unless you have real nice Bosch Halogen like I do. Maybe now is the time to upgrade!..But like planetman said you could try unhooking the spades inside the plug or you could squirt a bunch of wd40, or penetrating whatever in there and work the bulb off the plug, it's just green corrosion holding it on, mine were prettty hard to get off the first time. BTW a litlle movement means you will get it of, side to side in and out, and jsut because it starts to come out is no reason not to keep going in as well this frees things up more.It is the same with nuts and bolts, if a seized nut starts to turn don't just keep going go back and forth back and forth this allows the threads toclear themselves of the corrosion a little and saves you from stripping or breaking the nut/bolt/electrical connection/whatever. Since you are considering getting a new plug anyhow nothing lost. Also any decent auto parts store has the 3 prong plug as this is a very standard bulb, DT21 I believe (can't remember as it has been years since I bought my Bosch lights and they have been flawless), anyhow pretty much the most common round headlight made.
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Patrick, '68 220, '92 Eurovan (work truck).