does anyone know if it is difficult to change the upper left motor mount in a p10?
do they have motor mount inserts?

and about how much would the mount cost?

Are you talking about the front mount, on the passenger side by the pullies? if so it's not too bad as long as you have the tools. There are no inserts for it, it's liquid filled, and i think they are around $50-60. But that also depends where you buy them from too. Hope this helps.