My power steering lines are leaking from corrosion. Is this expensive repair job? 
Driver
I don't think this is a common problem. Can you provide photos or more detailed description?
The high pressure line is pricey, but check Rock auto.com for the hoses....They seem to have the cheapest ones....As for replacement, the one line should be straight forward, the other kind of wraps around the body, I believe it goes to a cooler line.
Driver
Depending on the cost for an OEM part it may be more reasonable to go to a hydraulic shop and have one fabricated.