I guess it depends on the cost of the doohickey compared to a new GPS. Lowrance are good units, and the 500 is OK - I think it is a $399 unit brand new. I have found the Lowrance screen redraw to be quicker than Garmin in many ways. Luckily, it's not too basic, but even a basic unit will do much of what you need.
If you can get the proper support, I would stick with it for a while, especially if, as mentioned, you can buy the Jep cards.
Phil