The M103 2.6L is a bit notorious for headgasket leaks, resulting in coolant/oil mix.

At 150K miles, I'll bet that more than just the struts need refreshing in that suspension.

A/C compressor leaks are also not uncommon with the Nippon Denso units. New, they can run up to $1K to replace.

As for the timing chain, chain stretch is not so much an issue as is a worn tensioner.