Hey CJS welcome!
I am waiting on my dulcimer (christmas present) however, I do have experience with a similar controversy in the banjo world. To play in C or G... or the many capoed variants.
I just started playing in C and by learning those fingerings G came along with no time at all. I assume the dulcimer will be similar.
Also, play the songs ultra slow making sure each beat is right on. Then move up in speed. Soon you will be ripping through them... at least that is how it is on the banjo. Patience and perserverance (which it sounds like you have both) is the key.
Enjoy the music for what it is worth.... not for what you perceive your playing is worth.