When I changed mine, I had a hard time getting it out because some lines were in the way. What I didn't know was that there was fuel leaking out the entire time because I didn't take off the fuel hose that runs to it. Needless to say, it was a mess. It might help to put a bag underneath the spin-on when you take it off to catch any leaks, if you are concerned about making a mess.
I had to go back and take it off again to fill it with fuel the next day, and this time when I took off the fuel hose to plug it, it barely leaked at all. Oh well. Must be a gravity issue.
It might also help to crack the fuel lines at the injectors to get some of the air out if it takes too long to crank. Luckily I have a good battery!
..I learned from my mistakes!

__________________
Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k