Soak the sh!t out of the area. Both the nuts holding the sending unit in AND the fitting from the sending unit to the flexible fuel hose.

I managed to get my sending unit out with 4/6 studs intact, but the hard neck on the sender cracked through and the hardline under the car broke, so I am now running a full S/S -6AN setup from sending unit to rail (and -8AN from rail to AFPR). It's actually not that pricey to do, but it's a whole lot better when you plan to do it instead of being left 'stranded' because it broke.

Summary:

1) Soak the sh!t out of everything with some sort of PB Blaster/Penetrant/etc.
2) Be fully aware and prepared for the fact that stuff is likely to break. (Hopefully it doesn't though).