Do a little searching on the horizon web sight and you can probably turn up a manual for the plane which will give you a center of grav. for the plane.

check the batteries by turning on and "exercising" the controls every couple of minutes for about an hour, then measure with a volt meter. Reciever batt. should read at least 4.6 volts. If not you should probably replace it. Transmitter batt. should read around 9.0 or better. Batteries tend to go bad after setting for a while but can be replaced cheaply.

When I get ready to run an engine that has sat up for a long time I pull the glow plug and the back plate off and immerse it in kerosene/WD-40 mix for a while to make sure all the "crud" gets cleaned out of it then reassemble and run at a rich setting for a tank or two of fuel to loosen everything up again.

You have picked up a real find at a good price. The Extra Easy is an excellent flying plane and easy to learn to fly with but be warned, Hanger 9 no longer has parts support for this plane so if you give in to temptation and try to fly it on your own you may be back on the sidelines again looking for another RC plane.

Good Luck!