The window stool of one of our basement windows is rotted and I have a
couple of questions on how to replace it.

The window frame itself is site built and is surrounded on 3 sides
(U-shape) by a 150 year old stone-and-mortar foundation. The exterior
side of the stool has rotted away so I need to replace it.

My plan is to knock out the rotten 2-by-X stool and replace it with
new materials.

Questions:
- Should I use pressure treated 2-by-X or is it OK to just use primed
and painted ordinary stock?

- If I do use pressure treated stock (ACQ probably), can I paint it
and if so what special preparation (if any) is required? (one guy at
the local borg store said I need to wait 3 months for the wood to
dry before painting)

- What do I use to secure the new 2-by-X stool to the foundation? I
would prefer not to have to nail or drill into the old rock
foundation. Is there a glue, caulk, or foam that will do the trick
of both sealing and securing the stool to an obviously irregular
stone masonry surface? (I could add a little mortar to cover any
gross imperfections)

- Anything else I need to worry about?

Thanks!