Precision Plating in Burwood. Haven't used them personally (got my own plater I use in SA, but my mate has and gave them the tick of approval in terms of quality/price).

About the only place in Melb that will plate plastics as well.

The chroming itself won't set you back too much depending on the quality of the substrate to begin with (rust, dents, chipped/pitted etc). As Strangeways said about $40/leg, but if you want to see yourself reflected in the leg it will cost more for high level polishing (labour costs).

Leg straightening shouldn't be a problem, but keep in mind the more they have to do to the leg to get it to "chromable quality", the higher the cost (labour cost again).

Price really depends on the finish and what you want in terms of the final product.