[VAL] removal of tub and black tank

[Nancy Phillips <nphillips@xxxxxxxxxxxx>]

My husband are the "proud" owners of a 1963 Globetrotter that will need
some work before it hits the road.  We are in the process of taking out
the bathroom so we can check out the flooring in that area.  After much
puzzling  we are left with the bathtub and fiberglass deck over the
blackwater tank.  We have read past posts, but didn't find the info we
need.  So here are the questions

1.  How do you detach the tub from the drain?  A post said to unscrew
the drain???  Just how do you do that.  From underneath somewhere?  from
the top, but how?

2.  It appears that the the blackwater tank is attached to the
fiberglass shelf that the toilet sits on.  How do you lift this out,
since it is not budging?  Do we need to do some work underneath, but
what?   Also there is a black vent pipe in one corner that goes through
the whole set up.  Do you need to cut it off, unscrew it some how, or
something else.?

We would love some tips, so we can finish this "extraction" this
weekend. Then we'll know how much more  we need to take out - closests
and kitchen. The couches are out.  Thank you for your time.