You don't have to delete NWC 1.75 when you upgrade. You can simply install noteworthy 2 alongside it as it goes in a separate folder so you can download noteworthy 2, install it and test it while still having 1.75 available should things not work out.

I can see no reason why your existing piano keyboard will not work with Noteworthy 2 as long as it its output conforms to the midi standard.

If you are unsure about anything, sign up for the forum on the Noteworthy software site and put your queries there. There are plenty of much more knowledgeable folk there than me, including the Noteworthy person himself and they are very helpful and won't put you down.

So why not go ahead and give it a go.