You do not HAVE to use that kit, if you haven't had problems with the water dripping out of your shift cable onto the engine, Then it's really not that necessary. Especially in fresh water.
I'm going to be running in salt water and dont know if it leaks but while i have everything apart i'm going to change that seal. Thanks for the # Don. Everything i can do now will eliminate possibilities if i have any leaks or problems when i launch her in the sring.