For A, the only option is really a bottle of fluid with an anti-leak agent. I don't know of anybody that fixes power steering pumps apart from aftermarket suppliers that refurbish them. But the way that works is you buy a new refurbished pump, and when you give them your old one, they give you the core charge back. Have you checked the fluid level? Maybe it's just got a leak and it's low? I'm not sure I've ever heard of a power steering pump that is quiet when forced to work hard.
As for B, maybe. You really need to compare apples to apples. The dealer will probably quote you list price for a new part (which is not what they're paying for it, just what they want to charge you for it), something pretty close to what came from the factory if it's available. It sounds like you're pricing refurbished aftermarket parts. You also need to clarify whether the dealer price is parts only or parts and labor. Repairpal says $431-$568 parts+labor, $120-$160 labor, $306-$408 parts for my locale. You can get the best prices buying your own parts, but trying to find somebody to install your parts for you while still warrantying the work is tough, though it can be done. I guarantee you'll pay more on labor, depending on the markup sometimes you're better of just paying it. It's always good to know what you could get it for yourself (Though again, apples to apples). Just walk up to the parts department and ask them for a price. It should be pretty close to what the service department quoted you for parts. If it's not, something is rotten somewhere.
As for C, expect the part to fail as soon as the warranty expires. Always go for the long / lifetime warranty when you're paying for a lot of labor.