About to get my first road bike - Any advice?

Start with the bars at the highest point - even, invert the stem - then gradually lower them over the coming weeks. That way you can get used to the new position slowly, step by step.

Regarding fit, this worked for me:

http://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp

This outputs three different settings depending on the style you might like. I am happy all day on the bike with their 'Competitive Fit'.

All my bikes stay out in the cold, never affected my racing. So no.

If you use it with salt on the road (even on dry days) it will get salt on it.
I as many have a dedicated winter bike but even then I wash it directly after every ride to remove as much salt as possible. The bike still deteriorates but less so.

As for positioning, try this;

http://www.bikeradar.com/fitness/article/how-to-get-your-seat-height-rig...

It sounds like a lovely bike, a real bargain.

But winter roads will wreck it in no time at all; the salt, the muck, roads that are constantly wet, etc.

Mudguards (though necessary) don't help. All that muck and salt is caught by the muddies and drips back down onto the brakes. You'll go through brake blocks and rims in no time. Keep it for summer (Mar to Oct), use the hybrid for winter (Nov to Feb). Most roadies have two bikes, their pride and joy summer bike and an old heap (in comparison) they use for winter.

Generally ride on the hoods, not the drops. More comfortable and actually more aero if the position is right. Riding on the drops gives you more control in fast downhill and sprints etc.

If you intend to do a lot, get a proper bike fit it is well worth it and you will reap benefits from a correct position.

Ride it a lot?

Actually, ride it to work. You'll get used very quickly.