91 Hatch STD, My battery light is constantly on and using a volt meter at the battery terminals with the car running i have a solid 11.9V or less and dropping, Is there some testing i can do before i replace it as pulling it out does not look like a 15 minute job lol. Also, Is there any benefit in installing an EK Alt with a $10 adapter plug or should i stick to the EG alt thats in it now?

 

Your right, it's a 20min job with the right tools at hand.
Things I would suggest to look into- First thing is just to make sure your battery wires and ground wires are in good condition. Start with cleaning battery post terminals of oxidation then reattach pos/grnd leads securely, then onto the battery to chassis, chassis to engine grounds making sure they are on clean bare metal and snug.
I would do all this to just make sure the alternator is able to recharge the battery with out the possibility of poor wiring/connections.
If the light is still on after this simple maintenance check, then pull the alternator. You could also look into just replacing the brushes as they may be just worn out. If you can source new ones, they are fairly cheap and easy to replace. Could possibly net you quite a few more years out of the old alt. if the bearings seem pretty smooth when you free spin it.
Lasty using a ek model will have no benefit. Only if you have something drawing quite a bit of power like a large audio system then you want a higher output unit and possibly additional batteries.