Stick to heavy compound motions. Bench, squat and deadlift variants as well as military press, good mornings, rows and pullups are pretty much all you really need to be doing. I'm not sure how I feel about olympic lifting yet, largely because I really haven't done that much of it, but if you have adequate instruction, I doubt they could hurt all that much. For grappling, grip work and ab work go a long way. I do sledgehammer levering excercises, plate pinches and towel pullups for my grip, and I've been doing alot of hanging leg raises and saxon side bends for my abs. Neck bridges are great too, but don't do them unless you can get someone to show you how first. It's kind of hard to pull off a triangle choke in a wheelchair.
Alot of people have alot of opinions with regards to set and rep ranges. I stick to heavier weights and lower reps. The most important thing to remember is to make the bar move as fast as you can without sacrificing form. If you are training to increase your explosiveness and power, you really don't need to be worrying about time under tension. Any excercise that can be done standing should be done standing. Leave the machines for the metrosexuals.