No need to remove the cowl for a head-gasket change, unplug the spark plug lead, the hose from the decompression valve, undo the 4 bolts holding the head on and it will come off.
Clean the old old gasket off the block with a scraper, clean the head GENTLY (its only alloy its soft) I use a careful hand with a scraper, and chip away at the gasket.
Reassemble everything with a new gasket, do the head bolts up in a criss cross pattern, I usually torque them to a point where everything mates up and add 1/2 to 3/4 of a turn.
