Designing Kitchens and Bathrooms - How deep am I

With a lot of help from the good folks here I finished remodeling one bathroom. Thank you!

Yesterday I started on the master bath; ripped out the carpet from the main area, linoleum and the underlayment from the smaller "room" that houses the toilet and shower. Found mold along the edges of the shower base and the toilet flange. I was expecting to cut out the subfloor around the flange but now it seems that I have to go beyond, way beyond, that.

My assumption is that the plywood subfloor does not stop at the edge of the shower base. If that is correct, the mold probably does not either and neither do the water marks.

My head is spinning and I have many questions. But before I expose my total ignorance by asking stupid questions, I would appreciate any help with an approach to ascertaining the extent of my problem (hows are important!) and possible ways of dealing with different possibilities.

FYI the shower walls are tiled and that, it seems, makes removing the shower base to evaluate the situation or to remedy the situation difficult (in my mind).

HELLLLP!

This is easy for me to say, but, what the heck. You might as well go for it! Unless you don't plan to be there long. I'd just start ripping out, and ask the questions as they come. You'll probably do a better job of putting it together than the folks who put it in originally did!

We redid our bathroom last year. It started out small and
of course it escallated to taking everything out down to the
studs. We had tiles up around the tub/shower and some of
them were loose. We decided to go with a tub surround.
It has worked out great. Lot easier to take care of. Bought
a newer tub and shower doors. Make sure the tub has
enough support underneath the bottom, so it doesn't give
in the middle when your taking a shower.
The projects can be extensive but the end result is better.

You are correct about the floor going under the shower pan. Is your wood soft or just stained? Do you know for sure where the water came from? If it's from out side of the pan, you're probably looking at the worse damage from it. The mold usually can be killed with bleach, it seems that the bleach solution would flow where ever any other water from outside the pan flowed. Let it dry for a long time. If it's from under the pan, you're probably looking at the least damage. Can you get under the subfloor and look at it? If not, it looks like you're going to have a normal spend alot more than you'd planned bathroom remodel.
Hope this was some help!