Julian,
Can you grab ahold of the fan and turn the engine over by hand?
One thing I learned with my last engine "wake up" experience is that just because a motor isnt absolutley stuck, it dosen't mean that it isn't slightly stuck.
I'd take the starter off all together, and hook it to a battery and see if she spins. If the starter spins free and fast, then the starter is probably fine.
Pull all the plugs and dump some penetrating oil down the cylinders and let it soak for a couple days. I usually just spray WD40 down there, but I hear that PB Blaster or Kerosene works even faster.
With the plugs out, and the transmission in neutral, you outta be able to turn the engine over by the fan with great ease.. don't even bother trying to start the engine till you get to that point.
