I personaly would not concider this a first time DIY project and would hire it out. I've done it many times because we did nothing but work on 100 plus year old homes and churches for many years. It's going to require several HD jacks that once you buy them you may never need again, you have to know where to place the beams and jacks, just how much to lift them at a time ect. ect. Done wrong and the walls above will crack and all the doorways will be out of wack.
You did get the place treated with boron to kill the powder post beetles, right? I also would suggest getting a termite treatment.
Wood does not just rot on it's own, did you find out what was causing it?
Without someone being there to look at this it's near imposable to give you the correct advice, every situation is differant.