I did a posting on my experience replacing the cells on my 1989 560SEL. Do a search by my username.
I agree it could be easy to cross thread, especially if you are laying on your back in the driveway, not on a lift. Also, ensure you have metric line wrenches, as it is easy to strip off the fittings. Have fun!!

__________________
1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)