Hi Dehager - welcome to the gang! You've made a wise purchase!
On to your questions: First, 6 1/4 oz of wood is not really too much for an 8 lb butt, but you could certainly get away with 5 to 6. Your pork butt will only absorb smoke until it reaches around 140-degress; after that, the smoke collects on the surface (this is what causes people to think it's "too smokey"). Another thought - if you know you really like apple wood for pork, you have a winning plan. I find apple to be a unique taste that people either like, or don't. I have switched to hickory and cherry for pulled pork to give a more "familiar" taste. Just my 2-cents...
Secondly, you asked if the wood would be enough for a "4 hours smoke." Make no mistake, your 8 lb butt will take more than twice that time. Figure anywhere from 1 to 1 1/2 hours per pound to hit 200-degrees on a butt for pulled pork! Plan accordingly! When you hit 200 internal, make sure you double-foil wrap for about an hour before pulling. This is important!
The key to good Q is to focus on internal temp - not time - and be patient! ??? Fortunately, patience comes easy with these smokers because you don't have to constantly tend to them and babysit! Put that rascal in there tomorrow morning, plug in a thermometer and don't mess with it until it hits 200. It's like the BBQ "Easy Button!"
When you can, post some pics of your pork butt, and give details about your prep and cook - we LOVE details!