Can an executor sell the house if the beneficiary doesn't want to?

The answer to this question depends on how the will is written, but the answer is probably "yes."  Most wills give the executor a great deal of discretion in how to handle property.  In addition, it is sometimes necessary to sell a house in order to pay creditors or distribute shares to beneficiaries. 

I suggest that you speak with a probate attorney in your area about your specific circumstances to see if there is anything you can do to prevent a sale of the house.