I changed a
finger board once. TO do it properly and professionally, plan on it taking a week if you work in your spare time. Radiusing the board isn't a big deal actually.It's more time consuming to properly shape and blend in the edges.
In other words, there's no such thing as buying a finger board that is cut to size and gluing it on and you're done. But you can buy a pre made finger baord .There are two **** sellers selling good finger boards of various
scale lengths. You'll want 25.5" scale.
If you buy a pre slotted finger board, it will be longer and wider than you need.Probably thicker too.IT must be located on the neck and then you'll get an idea of how much material you need to remove. But it is certainly something that a master luthier can do and it wont be cheap.