Do a bit every day , dont go to hard to early you will just burn out or get sick of it.Half hour exercise every day will do it to start , dont eat less just eat better , at your size your obviousley a naturally large dude , just change the lard to muscle mass , get into lifting heavy the basic compound exercises.And lots of walking , at your weight you dont want to be pounding the pavement you will just bugger your knees and hips

If you like punching stuff , go to a good boxing gym when you have a good base going , nothing like boxing training to strip the fat

Good Luck , oh and get on a 666 and paddle a river or creek.