I have a detached garage that I plan on having the siding replace in the
near future. It also has a window that needs replaced. This is the only
window on that side of the garage. Because the size of the window (23" x
23") is non standard, I would rather install something that Lowes has in
stock.

Can I simply reframe the opening to a larger size and install the new
window? Any info on the internet about reframing window openings or is
there not much to be concerned about?

Currently the siding has 'paper' underneath it. I understand that it would
be wise to install OSB. I would like to remove the siding ASAP so I can
install the window, but it will be a few weeks before siding will be
installed. Would it be ok to install OSB and leave it exposed to the
weather for approx 4 weeks or should I cover it with plastic or something?

Many thanks,
-j