how do I change the seal at the engine side looks like the bolt to remove plate to change gasket is not accessable.....
Oil leak at engine seal for oil filter lines on 1991 Chevrolet S10 Blazer
You didn't say which engine you have. By your question, I'd think that you have the 4-cylinder engine which has a steel cover on the side of the block for access to the cam followers. You have to remove whatever is in the way or work around it to get access to the cover.
4.3 6 cyl. adaptor plate on engine leaking can not get to access bolt that holds the adaptor plate on engine sup and return line