how do you change the rear main valve seal?

[phildaddy]

i am leaking oil from my rear main valve seal and im new to workin on cars and dont know how to fix it if you could help it would be awesome

[RicardoS]

[strutman]

oh that job is horrible, the z5 is notorious for rear mains going out, i believe mine is starting to go, it's bad, i get scared just thinking about it.