Honda Pilot Transmission Repair

I have a 2003 Honda Pilot with 140k miles. Recently I had pressure switch repaired in the transmission because a rumble occured between 1st and 2nd gear. Shortly after the repair we noticed an engine oil drip so we took it back to the tranmission repair shop and they said the rear main seal was starting to go and would need to be replaced…to the tune of $800 - $900. My question to you is, could the first repair from the pressure switch have caused the seal problem?

No. Replacing a pressure switch on your transmission has absolutely nothing to do with the engines rear main seal leaking.