Matt:
Just depends on how you plan on riding your bike. For regular "cross-country" a 100mm fork is fine... perfect in fact. If you plan on doing some gnarly downhill, or more "all mountain" you might want to consider a 120 - 130mm fork but I'm uncertain if your bike is designed for such a large fork. Generally the fork the bike comes with is what the bike is designed to take.
There is some debate on whether you should ride with V or disc brakes. Generally people have hardtails because they are lighter/faster. Adding disc brakes adds some more weight and can slow the bike down (personally I'm not rocketing down anything so like my disc brakes).
I would really take your questions to a reliable bike shop or mechanic and see what they recommend.