Since they didn't come out with the change recommendation until I had 24,000 miles on mine, that's when I changed it (the rear had gotten the 600 mile change), and the oil I took out - into a clean cooking pan - looked exactly like what I was putting back in. No sign of deterioration that I could see. I personally would be quite comfortable with 24,000 mile change intervals.
As far as paying someone - well - you can. We try to make it easy to avoid that with the DIY's, but I can accept some people simply don't like or want to work on their own bike.
As far as them knowing when they sold you the bike - I think you're wrong. An old saying "Never attribute to malice that which can be explained by incompetence" - and I believe that's the case here. If you're really unhappy about it - there are lawfirms specializing in class-action lawsuits. Not that I'd do it - but that option is out there.