Water-Oil Cooler removal

I've just done the head gasket on the Cabbie, all skimmed and lovely.  However, I have now found the same old mass of gunk in the header tank and in the rocker cover.  
I am hoping that there is nothing more serious inside the engine, and that it is the Oil-to-water cooler that has given up the ghost.  Is there a way of checking if it is this?  Can it be bypassed or anything?
Also, I might be being incredibly thick (at a wedding last night - bit hungover!), but how do you remove the cooler unit?
Cheers for any help…….

Remove the oil filter then undo the large nut - I think its 1" or something around that size. Also disconnect the 2x coolant lines. You could bypass it but you'd need to fit a shorter tube for the oil filter housing and connect the 2 coolant lines together, eg with a U shaped tube. They're cheap enough to simply replace if suspect.

Thanks Paul - I did wonder if it's easiest just to replace it anyway.  I'll get on to GSF on Monday…………………

only way to check it is to disconnect the coolant hoses and bridge them together, thus bypassing it. if oil doesnt come back it was the cooler. also you'll likelty see steady drips of oil out the cooler pipes.

to clean the gunk out, drain the system and flush with hosepipe as best you can, then refill with plain water and put in a cup full of bio washing powder.  run engine till hot, allow to coolthen drain and flush again.  repeat till oil gone

refill it with plain water at first, since its nice n warm out no need to worry about it freezing and if you only run it for a week or so to proove if its cooler or not shouldnt have any issues with corrosion.