You really need to contact a vet about when to start vaccines. It usually depends on where you live. Typically vets will vaccinate 1st rounds anywhere from 3-6 months. Right now your foal is getting antibodies from momma, but still needs to be protected from rabies, encephalomyelitis, things of that nature. Like I said, discuss that with your vet.
As far as weaning, I usually wean at 5-6 months, depending of the foal. I start weaning very slowly ie, putting mom on the crossties (right out side her stall) and brushing her, while foal waits in the stall. Then i'll move mom a set of cross ties a little further away. When the foal is okay with that, I'll take mom a way for a few mintues, hand walk her around the ring a bit. (keep in mind that someone should ALWAYS be around the foal when you do this in case some thing happens) The idea is that the foal gets used to being without momma for a little, but knows that she'll be back. Then one day...she doesn't come back. It makes for an easier transition for all. You can expect some screaming and some bad behavior, but not nearly as bad or as lenghty if you just rip them apart.