2006BLKMegacab

my neighbor has a 60 series in a 98 freightshaker, its been parked for about 6 weeks after he got done hauling grain until he started it the other day and now it has an oil leak from the gasket between the oil filter head and the block (or in the area if its not the gasket) it was on Ontario truck so its fairly rusty but my question is this, how big of a PITA is it to get the filter head out of them? is it possible to get the filter head out the bottom without draining all the coolant or does the cooler have to come off the top of the filter head and come out the top?

Thanks in advance guys!