I have a century built stg with an imbel receiver that works great. From what I have heard, it is either hit or miss with one. The ones with the imbel receivers are more desirable than the ones with the hesse receivers due to the fact that most hesse stuff is junk. If yours works, you got a great deal, if it doesn't well, it might need some work.
The one thing with the century built FAL's that causes people the most problems, is the gas piston. It is a two piece piston and if it is not straight, it can cause problems with functioning. Check to make sure it is straight by rolling it on a flat surface and see if it wobbles any. If you do have a bad piston, you can get one piece pistons from Tapco or DSA that will work.
If it has an imbel receiver, then most likely their won't be any problems with barrel timing or headspace. However, it does not hurt to check the headspace first, just to be sure. If the gas block/front sight is not slanted and the piston doesn't bind entering the receiver, then you should be good to go.
One last thing, make sure when you first start to shoot it, that the gas adjustment ring is up against the front sight on the 1 setting. If it functions fine on this setting, then turn it out until it fails to function to find its highest setting. General rule of thumb is to turn it back one full number from its highest setting at which the rifle will function reliably.