Need help deciding what to do with likely mold

We've had mold/mildew growing on the shower tiles, mostly along the floor of our shower since we bought the house in August. We clean it up, but it eventually comes back. I've always thought this was because the floor at the front of the shower does not properly angle towards the drain, allowing water to pool there.
The fan is also probably inadequate for the bathroom and it's clear there's at least some moisture problem as the curtain rod left by the previous homeowner has rusted a bit.
We've also got some black spots on the ceiling.
When I went to remove the grout this weekend (some of the grout on the floor had failed), I discovered the grout in that area where the water pools was saturated and water had infiltrated back behind the tile. It appears there's some mold growing in that space near the floor, but one row of tiles up, I don't see any mold. I haven't removed any shower floor tiles yet.
We've already come to the conclusion that we need to pull off all the tiles, replace the backerboard and retile, or install an enclosure.
What I need to have some guidance on is whether we should have a professional come in and look at potential mold issues, or if we'd be safe in doing the removal ourselves until and unless we see obvious signs of widespread mold infestation in there.
The spots on the ceiling are bugging me a bit, as well. I don't know if that indicates the mold has infiltrated the drywall in the ceiling, or if that's just surface.
Any help anyone can provide would be most appreciated. We're trying to decide on a course of action and get to work as soon as possible.
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snipped-for-privacy@gmail.com wrote:

That's a tough one to answer. If it is the bad mold, you do want to know about it and take aggressive action. On the other hand it is not often the bad mold. I would suggest that if you are not experiencing any reactions (like lots of colds rashes etc.) to the mold by now, it is not likely to be the bad stuff. I would work on the mold and not worry. I have seen some really bad mold and it was tested and found that it was all OK.

What overall condition is the drywall. If it is marginal, I would just tear it out and replace it. If it is just a very minor spot, I would treat it and paint. Neither is a really bad job.

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Joseph Meehan

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The drywall seems to be fine. The spots are only on the ceiling. I haven't noticed any bulging and the paint is in good shape. It looks like it's pretty much on the surface to me, but I'm a new homeowner and this stuff is all pretty new to me.
We haven't pulled the wallpaper off the walls yet, so I don't know if there's anything behind there.
I can't say we've noticed any health issues. I'm mildly allergic to mold, and I have been stuffy lately, but oddly enough, winter is my worst allergy season, so I can't say anything is different than any other winter.
My inclination is to just pull all the tile and backerboard or drywall, whatever's back there, off and, assuming we don't find mold colonies behind the wall, replace with hardibacker or greenboard and retile.
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How do you get rid of the mold, bleach works best. I just keep a spray bottle handy with bleach in it. Mold needs food to grow, cleaning off the soap residue will retard its growth
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Unfortuntely you will not really know until you get everything removed what the problem may be. You could get lucky and find that once you have removed everything to the studs and ceiling framing you have removed the problem.
You could start spraying bleach after each shower after you wipe down the walls and floor. To remove all of the water.
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