| Is there any problem in putting water-based polyurethane over oil-based
(if
| that's what I have)?
|

I'm afraid I can't help with that. I've never
used the waterbase stuff except for new cabinets.
(I can't say I'm impressed with it, though it does
settle down pretty well.) As for bond, sanding liquid
makes the old poly as though it were put on yesterday,
so you're doing another coat of the same finish, in
a sense. It works great for any oil-over-oil use. I don't
know how that relates to water-base finish. In that
case the sanding liquid may not help. It may even be
worse, but I really just don't know.