Lead poisoning from paint & such is not normally a problem with mature adults. Major problem is with pregnant women & young children. At least that is what I was taught many moons ago in my job. Critical time is in the early development time of a human's life.
Like someone has already said unless you plan on eating the painted substance.
Apply a good coat of paint remover, then scrape the bubbled up paint and remover off. When I did stuff like this, I scarped the crap off into 5 gallon plastic buckets. Allow the wood to dry completely, then use cabinet scrapers to clean up the rest of the paint and crap. Good scraping techniques and you will only need minimum sanding. Andy and all sanding of any paint residue is left should be done with mask etc and outside with no kids around.
These old doors ca be made out of all kinds of wood, including different types of wood on one door, the staining can and probably will be a "witch" to get done so that they look good, or they can be all of one kind of wood and be easy. Try the stain your stain on hidden areas, like the tops and bottoms to see what you get.
Sometimes I cheated, and I would use Fiebings alcohol based leather dye as a wood stain. They have every color and kind of wood color under the rainbow. It can also be diluted so you get a lighter color of stain, or you can add some black and get a darker stain of the same color, or you can mix say a yellow and brown and get a golden looking brown. If you go this route, KEEP NOTES of every mix you create, you will eventually need that "formula" again. The real bad part, once applied, there is no turning back, this stuff soaks in, you would have to sand away an 1/8 to 1/4" on both sides, leaving and awful thin door.
Find a few pieces of pine 1x12 that has some grain showing, apply a coat of diluted black Fiebings, then sand it with medium grit to remove some of the dye, then apply a walnut color stain. This will show you how to emphasize the grain by using a darker color first. Might want to research double and triple dying and staining wood. The best part about Fiebings, if you have done your homework you create some awesome looking pieces of wood.