The less fuel the better, 1/2 tank or less.
Sock is same.
Pump sits in a barrel type holding bracket that attaches to sender unit.
I have done two(Bosch in tank pre-pumps, same operation) and soldered neither. Just two tiny little nuts with lock washers that attach wires to the top of pump, tighten well and forget 'em.
Use the rope trick where you pass the rope down thru the return hose hole and use it retract the sender. Depending on the type of low fuel collector apparatus at the bottom of tank, centering the sender will either be real easy or real hard. My 92 had a collector which was significantly less tall so swinging the sender into position was a snap and required little retraction.
The 94 940 had a much taller collector in the bottom of the tank and this made proper positioning a real Bitch. Dont bother trying to work the clamps loose if they are original, use wire snips and cut em off or use a dremel with cutting wheel. Dont worry about the fumes, just use common sense.
Good luck.
Matt