I know this is hind-sight but if there was a suspicion of lead paint, the buyer may have been able to 'work' in the costs for its removal into the sale contract.
Anyway, here on the east coast, Seller Disclosure forms are more and more becomming mandatory for the seller in many states. This is a question on the form regarding this, and if the 'current' owner at the time is not aware of any lead paint, that could be true when you see the answer-box checked "No". BUT, when you see that question asked, it ought to be a hint that it ought to be looked into first before buying. The same principle applies to the questions regarding things like water in the basement, termites, etc., etc.. Unless, however, the buyer is aware of all the potential problems AND is willing to deal with them on their own.
As for drywalling over the lead paint, that may not be legal in CA. And again, if the question comes up when the new buyer goes to sell, "Are you aware of lead paint in the home", and they say "No", and the future-new-buyer may be able to prove that the owner DID know about lead paint (because they covered it up AFTER they bought the home), a law suit could be filed. It's a chance that one may take but buyer and seller beware! So, what does one do about the lead paint on windows, doors, trim, cabinets, etc., etc.? They can't be drywalled over. There are methods that are costly and methods that are less costly but time consuming. My suggestion is this: contact the EPA for printed information about lead paint removal. Also, contact the local historical society for info too. I'm sure you're not the first person in the neighborhood to embark on this type of project. The experience of other folks goes a loooong way.
Just my $.02 on lead paint in the home. My best to ya and hope this helps.