89 cabriolet stripped engine block threads for oil pressure sensor

The head on my 1989 cabriolet was replaced approx. one year ago. Recent increase in oil leaking around sensor threads on rear of engine block. I question that
this (disruption of threads) was done at that time. Threads are stripped in block. Can I drill, tap, and use fix a thread or helicoil without disturbing engine oil or coolant flow, or worse yet, both? Also, what size would I drill and thread out to? Thanks for any help or advise that you could give me.
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On Monday, December 15, 2014 2:18:01 PM UTC-5, 89Guinea wrote:

Take it to a machine-shop and have them do it. All it takes is a few chips in the engine and the $$ you saved doing it yourself all go away.
Peter Wieck Melrose Park, PA
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