Posting some pictures is really helpful if you are looking for ideas. Maybe start with something small, one bathroom, and move on from there. One step at a time and it will start to seem less overwhelming.

You should start with the rooms that need the least work. Get them out of the way. Then you can spend majority of your time on the harder rooms.

Consult an architect or designer to come up with an overall plan of attack and also lets you see the full potential.

I'm an interior designer with a particular focus on healthy, comfortable homes. Your top priority should be preventing mold, because once it's there, it's a real problem. So preventing leaks, getting rid of plants that are too close to your home's foundation, and dealing with the indoor climate (heating and air conditioning) are all much more important than how the place looks.