Rear differential leaking from cover

[Damien8086]

A couple of questions (apologies ahead of time for my ignorance):

(1) I have a greenish colored liquid slowly dripping from the rear differential cover. Is this likely just a matter of taking the cover off and replacing the gasket or is there probably more to it? Do I need to drain the differential fluid first and if so is there a guide on here somewhere for how to drain and refill? Any gotchas or anything I should know before replacing the gasket if that is all it is? Are there stud kits for the 12 bolts and can I just use a fel-pro dry gasket?

(2) I noticed a rubber hose that appears to be connected somewhere near the front of the rear differential and the other end appears to just be tucked up in the frame. What is this for and does this look right (the hose just being tucked up into the frame like that?)

Thank you for any help.