Like everyone else said - Cardio! It's key.
Really you need a coach, someone who has fought before. A good coach can really keep your head in the right place even when it doesn't want to be there.
If you have a good ground game just try and get enough striking/boxing to keep yourself from getting knocked out. Learn how to hold you shoulder, head and the right way to move and keep good angles.
As much as people like ground game there is nothing like the feel of someones jaw breaking on your fist. Get that striking game up!
Train hard and you should do well. Also just running isn't enough for cardio. When I started BJJ I ran 1/2 marathons from time to time but got gased within 5 minutes of rolling/striking.
Lastly make sure you don't kill yourself cutting weight. Chart your progress everyday and tailor your diet accordingly. Try and eat as much whole natural foods as possible. A good nutritionist can go a long way.
Report back on your progress I am curious to see how you do. I got a fight comming up in 4 months - I still need to drop 35LBS for... ugh...