I've no idea what the white thing was but maybe it was just some sort of protective cover over the intake in the centre at the back of the tank? These are reed valve engines which means they're quite happy to run in either direction although it's not a good idea to run them backwards with a normal prop on them. It's best to use the Cox fuel in them because they need a fair bit of nitro plus a lot of castor oil. Never run them on normal RC fuel. The glow plug is the entire cylinder head which just screws in and you should have a special spanner which is used to dismantle the whole engine (I don't recommend doing it though ). Also, the plug is strictly 1.5 volts so be careful not to burn it out.

You should be able to free it up by flooding it with fuel and turning it over carefully until it gets a bit looser then flicking it over. When the prop starts to oscillate it'll be ready to run. A drop or two of fuel straight in the exhaust port usually gets them going but make sure the needle valve hasn't got any muck in it. If you look in the exhaust when the plug's connected then you should see an orange glow reflecting off the top of the piston.