hey guys, i bought a 36" exmark to mow my lawn bought it used for 500.00 lawn mower was in great shape. i just gave it a tune up.......fresh plug, new air filter, fuel filter, oil,greased most of the mower and got new blades on the way. since i did not by it new i did not get an owners manual, so i searched for one online and found one and it was saying that you need to change the grease in the transmission once a year. is this hard to do? should i attempt this or take it to a shop.....i am pretty handy but i do not want to risk messing something up in the transmission......is this really necessary?