Beauty is in the eye of the beholder as they say. You would never get your money back on a bike like this, but if you like it and you have the extra parts why not? What's important is you get out there and ride.
To switch to threadless forks won't be easy. First you will need a 1'' threadless head set and they are pretty hard to find, and when you do find one they are often pretty expensive. Some used cranks won't be hard to find. You will need a threadless stem as well.