The only way to know if the chain needs to be replaced or not is to measure the wear (stretch). If it is 5 degrees or more, time for a new chain.
See my post #6 here for a pdf document you can take to the mechanic for them to check your chain:
http://www.peachparts.com/shopforum/diesel-discussion/203770-timing-chain.html
I'm also attaching a picture that shows the cam tower mark and the camshaft timing mark.
I like to lay a ruler along all the cam towers, lined up with the marks (they all have the mark) and hang the end of the ruler over the camshaft shoulder timing mark, then look straight down using one eye and carefully rotate the engine until the marks are lined up.