W124 Upper Rad hose replacement

[Addbhp]

This is for a 1990 300e - I noticed a small crack in my upper rad hose, and want to know what is required to replace it so that I don't get air in the system. I have the replacement part ready to go, by want to do this correctly.

Also how do I test my aux fans, both are free to move by hand but car is running hot in traffic, no problem when moving. I am in Toronto Canada and it's not even summer yet.