Last month I bought a new gs. One week after I bought the bike I had to pay $260 for the 1st service. Now I have 3700 miles and I found out that ANY work not done by the dealership will void my warranty.

I like to travel a lot so I bought the bike to save money but paying $160+ every month for service seems kind of stupid. So would it be better to just do the work myself to save the money and risk the warranty, or bite the bullet and pay to have the work done?

The Magnuson-Muson Act (or something close to that) of ~1976 makes it illegeal for companies to require service to be perfomed by only them as a condition of warranty.  They can require that you prove that your actions, or lack there of, did no harm to the warrantied item.  This means that if you wish to retain easy warranty service, and yet not pay dealership prices, you should start a bike service log, follow the factory recommended service intervals and practices, and keep reciepts of all items used in servicing the bike.  They can deny warranty if you modify the bike, but they cannot make you use their service as a condition of warranty.