Unfortunately, the GPS in the KMD-150 does not comply with any of the requirements for GPS performance in the latest ADS-B mandate or DO-260B. More or less, although it is not specifically referred as such, current WAAS GPS receivers are the only GPS receivers that meet the performance requirement needed for ADS-B Out.

Considering your current situation, here are a few possible scenarios for you to comply:

1. Keep the KMD-150 with GPS as a stand-alone navigation aid and pursue the KGX-150 with internal GPS. This would of course require installing a separate WAAS GPS antenna on your aircraft for the KGX-150. In addition, you would not receive any of the ADS-B In benefits since the KMD-150 is not an interface for that. However, there are many options to display ADS-B In information on anything from smartphones, tablets, etc.
2. Replace the KMD-150 with some sort of Garmin GNS or GTN navigator which will meet the approved position source requirements for ADS-B. I would recommend their GDL-84 or 88 boxes for the UAT portion of the equation however there are a few other manufacturers offering less expensive UAT solutions like Free Flight with their Ranger Lite product.

The second option is obviously going to be more expensive but gives you a little more versatility and more capability in your aircraft. I only included UAT (978) options because I am assuming that you are flying below 18,000 feet.