Dave,

The headset board is a plug-in board and very easy to install.

Just lay the keyboard face down on a bed to protect the keys.
There are a bunch of Phillips(cross head) screws with several being longer than the others, so be sure to mark where those go.
When you lift the bottom up, you will want to open like a book because all the connecting cables from bottom to top halves are at the back of the board.
The headphone board is right there where the plug is located - easy to see and easy to replace. It may just have a bit of corrosion on the contacts.

Bill G