bad engine

What is your question?

Heard a loud sound then wouldn't start. tried jump starting no luck. Had it towed to a shop. They said they took the starter off and the engine was seized up. It has 154,000. Bought a month ago. New serpentine belt, timing belt, starter. Mechanic "thinks it could be the cam shaft? Does have a minute oil leak and have been closely monitoring it. Added oil after 3 weeks driving it. Should I have another engine installed and if so what year will fit. It is a 2003 Subaru-outback vdc-3l,h6(183ci)

What makes this problem better or worse?

Nothing not running

How long has your 2003 Subaru Outback had this problem?

3 weeks