Since I'm upgrading to a 20mm axle up front with a new fork/front wheel, I figured I'd look ahead to see what's involved with replacing the bearing. Since I already went through the process of overhauling my rear wheel, I wanted to see what was different with these 20mm front hubs.

Can I buy just any bearings that are listed for 20mm axles? Do I have to get a specific brand? If I have a Shimano hub, do I need Shimano bearings? A quick ebay search finds two auctions that appear identical, but the title says 20mm 6805 and another says 20mm 6804.

What's the difference? Also - how hard is it (and what tools are needed) to do this task?

Like I said, just trying to look ahead. Thanks!