First, we would recommend contacting a local Garmin dealer to discuss the following:

• Upgrading your existing nav/com to a used GNS-530W or the newer GTN-750.
• If you already have a Garmin transponder (i.e. GTX-330), then you should simply get the ES upgrade, interface to GNS-530W or GTN-750, along with a few other minor installation considerations, and get the shop to do the appropriate paperwork based on Garmin's AML STC.
• If you do not have the GTX-330, then you should just consider pursuing one of the GDL systems from Garmin. Most likely the GDL88 which will give you In/Out capability. Same interface and installation considerations as above apply. Please note ADS-B In is not required for the mandate.