It can be done directly through FCC.gov and pay the fee directly to them. But, I can tell you after doing several in the past, the $110 or whatever it is I paid to Cara Enterprises to do mine was well worth it. I had them also go ahead and reserve me a few frequencies on each license for use down the road to avoid having to refile. This worked good because shortly thereafter I got tired of listening to the pro shop and put them on a separate channel.
I did a quick license search and CARA is who set yours up initially.
http://www.caraenterprises.com/I've also had our local radio shop do it for me as well.
I'd avoid Business Radio Licensing because I too get their mail and consider it "fish" marketing since they are fishing for business. Their mailings look official and often fool many unsuspecting people to do business with them when otherwise they wouldn't need to. I'd hate to see what kind of junk mail we would get if we did business with them. The best one is the mailing they send where they want to charge you to confirm your license info is correct. What a scam.