It might be a bit hard, but you need to start with weight you can handel. I dont go past 85's or 90's because the technique gets sloppy after that much weight. And as for the leg drive.. yes its very important... try putting ur legs onotp of the bench while benching with a Barbell or DB'S. it works for me. It takes time to get the motion and movement down. Try these steps.
Step one- Grab the DB's and stand infront of the bench.
Step Two- Place the DB's infront of your Quads and sit down.
Step Three- Relax and breath, then keep them close to your chest and slowly lean back and keep your wrist straight andmove your elbows away from your body.
Step Four- Start the rep, remeber good form is the key.