If I were you, I would first try a new glow plug and make sure that you are using a good glow igniter. I have two and the one that uses a regular alkaline C battery really blows. It will light up the glow plug and get the engine started but it will die in a few seconds because it doesn't get it hot enough. Also, if I try to use my second glow igniter when the battery is dieing it will start the engine, but it will also die on me in a few seconds. What kind of glow igniter are you using?

Also, I've read that if it's hard to pull the pullstarter, that, that may be because the engine is flooded. in which case you shouldn't try to start the engine. I think what you do is take out the glow plug and turn the car upside down and let the excess fuel fall out into a rag through the glow plug hole. If you keep pulling you also risk breaking the pullstarter.