Well you've got a lot of choices ahead of you. Read through the treads on the forum and you'll get a lot of great ideas. Here's my two cents

1. Stay with steppers above 100 oz/in. You can pick 116 oz/in ones up pretty cheap and they will do the job for a time but if you can get more power do it. I'd also prefer to use bipolar motors.

2. For the driver I would suggest the xylotex, one because it's a bipolar chopper drive and that there are a lot of people using them so support would be good. You could go with geckos if you got some rather large stepper motors but they are spendy.

3. Linear bearings are costly if you go with THK's but they are super precise and super strong. On the other end is gass pipe and roller skake bearings. Look through the treads for ideas on what you want your machine to be.

You've also got several different choices for the power transmission, from (preloaded ballscrew to ready rod) for a first machine I would use acme rod with two nuts preloaded or offset to reduce the backlash. I think I've said enough to get the gears turning inside your head.