Yes, most of your MapBasic is the same as earlier.
It is mostly about how you integrate your tool into the interface that's different. Earlier you created menu items and buttons. Now you need to add your tools to the ribbon interface.
I'd recommend you to just try to run your tool in v17 to see if it works. In many cases it does. Sometimes you will find the features of the tool in a separate tab, in other times it will be found on the tool itself in the Tools window
The MapBasic window is still around and will still record and let you play back any MapBasic statements.