There is no trade-in program.
Most all the Navionics cards now are micro-SD with a SD adaptor. They have some issues for "off brands" that use a different format.
You can get the Navionics+ software for $99 MSRP by purchasing the Navionics Update card.
You use the current card to active it, then it becomes the Navionics+ version.
Then you can keep or sell your current card since it is still usable.
Navionics+ also includes the Sonar Charts program and has no maps. You choose what to download to the card from anywhere in North America--no regional restrictions like you have now.
MSRP of the Navionics+ is $179.
MSRP of the Hotmaps Premium is $149
MSRP of the Hotmaps Platinum is $199
Both of those are regional versions like you have.