Jeremy,
You did not say why you thought that your air dryer needed service. If you are going to service it as a preventive maintenance, the filters that Richard mentioned above will be all that you need, and it is a fairly simple and straightforward procedure. However, if your dryer is malfunctioning, like the purge valve is leaking or it will not purge when the compressor unloads, you will have a more complicated repair that changing the filters alone will not fix.
The service intervals that are listed in most owner's manuals for this air dryer are way to frequent for the service that we (Beaver coach owners) use them for, in my opinion. They were designed for trucks that drive 300,000 miles a year, not the 5,000 to 15,000 miles that we put on them. So what I am saying is that you should be conscious of this in servicing the filter, as over servicing the dryer is a waste of time and money. If a coach is operated primarily in a high humidity area, such as Florida, the dryer will probably need to be serviced once or maybe twice in the life of the coach. Where a coach that is operated in Nevada and Arizona will probably never need the dryer serviced.
Gerald