French lops are adorable! Congrats on your new arrival.
If he has just been neutered I definitely wouldn’t bath him. Clean him up as best you can with a damp flannel or towel, and make sure he is dried properly after. Once he’s in a clean environment he’ll probably do better at keeping himself clean too.
Since you’ve just got him, try and leave him in a calm and quiet area and not disturb him too much, so he has some time to settle in. It’s good to give him a box to hide in too.
With the fleas, there’s only one type of flea medication that is safe for rabbits (but I can’t remember which! If you search on here you’ll find other posts). I would also recommend a vet check up though, as sadly it doesn’t sound like he was cared for very well before you got him.
Have you had a rabbit before? If not, then the info section of this website is a great place to learn about best rabbit diets etc. And of course, keep asking questions 