You can try to modify the resort online at 8 am at your 7 month window. If what you want is available, it will replace the reservation you have. If it is not, then you'd just keep the original one. If you think you would be willing to split stay, then you'd have to wait until 9 am to call MS as changing part of a reservation doesn't work online.
In terms of points, the freed up points will be returned to your account in the same way they were used in the reservation. They will use up banked and borrowed points first for reservations that take less points, and leave you with your current UY points.
If the reservation, however, uses all borrowed points, those points would go back in your account still borrowed, and you'd still need to use them up by the end of the UY of travel.