1) No, you don't need to be physically present, so long as any one not there has executed (and had properly witnessed) a power of attorney in favor of someone who will be there, allowing that person to sign on their half. Ideally, share the POA with the buyer, buyer's agent, and/or buyer's attorney ahead of time, so they know that someone will be signing on behalf of others with  POA.2) If you are all equal owners, proceeds will be divided equally unless the four of you agree to some other split.