what goes into probate

Any asset that has a named beneficiary passes outside of the probate estate.  Payable-On-Death assets being a good example.

If the land and house were held in title by the deceased and another party as "joint tenants", then they too will pass outside of probate; if the property was not so held than it is included in the estate. 

As for the charitable bequest to the hospital, since it is a specific gift, absent state law to the contrary, the general rule is that specific bequests are paid first even if they deplete the rest of the estate.  That being the case, then yes you would have to sell the land and house to satisfy the gift to the hospital.  Any money remaining after the hospital was paid would go into the residual estate.

You should consult with an attorney in the area, they may know of something under state law of which I am unaware.

Any bank or investment accounts with TODs in place go directly to the beneficiaries.  Everything else goes through probate unless they are part of a trust.  After probate is complete, assets go to whom your mother designated as her beneficiaries in the will, including any charities listed.  If there are assets not designated, they go to the "residual beneficiary"--i.e. the beneficiary who gets the leftovers.  It is always possible that real estate will need to be sold in order to give to those promised either exactly what was promised or the cash equivalent of it.