[DennisAN]

With a lower miles car you might get away with just cleaning and re-installing your 3 chain tensioners. Check for posts on "boiling" the tensioners in a pan of hot Marvel Mystery Oil. They are about $120 each. But at your mileage....

Is the engine original? Many 1997 and 1998 Boxsters had their engines replaced. Check the engine serial number on the passenger side of the engine - it's pin stamped on a small raised boss. You probably will need to clean it to read it. Replacement engines have an X in the first few letters.