Should I be worried about coin damage?

My uncle gave me a "A Silver Story" a couple of years ago.
It has a silver cert, 1 oz silver "nuggets", 1 morgan and 1 peace
dollar.
I haven't seen the rev of the coins since there is plastic over them.
I have it on the mantle as it isn't expensive and it is nice to look
at.

My question is: Should I be concerned about PVC damage or anything to
the coins? I live in the pacific northwest so we have humidity here
and I think that is a negative as well.

If I should be worried about PVC damage, is there a way to keep the
items together and still have my nice thing to look at or should I
count it as a loss?

Thanks,

Ron