A.G.
You will likely gain weight, but really its not a big deal, if you are successful you will be gaining a lot more weight anyway. The effect will just be that you look pregnant a little earlier and that is a tiny sacrifice for a new baby. Also some of that is water gain due to the hormones (think bad pms bloating) and will go down. You will not be able to do any impact exercise at all from the implantation until your pregnancy test, and truly your expanded ovaries will be a little tender and vulnerable to torsion if you do heavy exercise once they get big. So you may have to just put yourself in the mindset that right now your body is for making babies, you can worry about looking sexy after your baby is born.
As for the mood changes, It wasn't too bad. I was a little crabby, and cried easily at commercials, but I wasn't a raving lunatic or a monster. Overall I felt fine except that I really needed to monitor myself for constipation and related pain from all the meds and take stool softeners before it got painful.