Congratulations on the baby.
The first couple of weeks are tough but amazing. Hang in there, try to ignore anything that winds you up.
My MIL really gets on my nerves, and even my wife admits that she gets annoyed when her mum says stuff like "well that's how I did it, and it never did you any harm". And we're just thinking, times have changed, it's been 27 yrs since you had babies, we are educated, we know more now that you did.
" Let your wife know that she is your babys mother and whist her mothers input can be valuable and insightful, she should do what you as the parents think is best "
This is definately something you should say. The baby is yours, not theirs, they had their time. They can have an opinion sure, but as the parents you have to decide what you want to do. (This also counts for know-it-all friends).
Don't forget to pay your gf/wife lots of attention, they will be all about the baby right now (and all the visitors will be focussing on the baby too), but they want to know that you're still interested in them (as well as the baby).