My advice is to spend the time with Audacity. You are going to have to invest a LOT of time doing this for your 500+ LPs. If you spend the time upfront, it will pay off later.
There is a reason
professional services charge an average of about $15 per LP to this. It's not for the faint of heart. erm, which is why I decided to just buy CDs for my most-loved CDs. I just don't have the time, nor the money to pay a service.
In iTunes, if the tracks show up as being from different albums, select all the tracks from the album and fill in the Artist, Album, track x of y. This article has good examples:
http://support.apple.com/kb/TS1468