Complex sentence: Luke initially only promises to take Obi-Wan as far as Anchorhead Station, but after he returns to his homestead to find his uncle and aunt murdered at the hands of Imperial troops, he takes Obi-Wan up on the full offer.
Split into simpler sentences: Luke initially only promises to take Obi-Wan as far as Anchorhead Station. After they return to find Luke's uncle and aunt murdered at the hands of Imperial troops, Luke takes Obi-Wan up on the full offer.