I had one.
And two of the other byron sabres.
1. It COULD be converted, but it would need very extensive modifications, and should only be done by an experienced person. It would need a LOT of reinforcement. Don't bother. Enjoy the plane for what it is, a great DF model.
2. Absolutely wonderful first jet. Flies like a *****cat, looks great in the air, easy to see. I miss mine.
3. In THEORY, parts are still available from Iron Bay Models. In practice, they really do not come up with the goods, they are impossible to deal with, and don't have much. If you are missing a major part like a canopy, call them first, ask them if they have it IN STOCK, and get the part in your hand before buying the plane. Otherwise, you may find yourself with a new model without a canopy, and any promises from Iron bay that they will be making up a batch of parts "sometime soon" are pretty worthless.
But as long as you have wings, tail, fuse, canopy, what else do you really need? Everything else can be made up.
Go for it, it's a great model, but what engine and pipe is in it? What price? What shape? What retracts?