Erwin,
On my 96 850 wagon, I used a Draw-Tite modulite wiring connector, and keep it in the spare tire well. I just hang it out the tailgate when I need to use it. Keeps the connector in much better shape.
I ran the power lead up the driver's side, under the sill covers- pretty easy. One tip if you are using a convertor with a separate 12V source- there is an accessory connector under the driver's dash panel. It is a 2-part yellow? connector. Your owner's manual should describe the various pin assignments. The male half of the connector block needs the terminal pin installed in the correct slot before you can use it. You can get this at the dealer. You should be able to figure it out- much easier than running the wire all the way to the battery. Use the slot that is 12V unswitched- since you want to be able to use flashers/parking lights when the key is off. I may have the part number for the connector pin if you need it. Take the other half of the connector to the dealer with you. Oh yea, use the ground screw in the back by the tailight.
Good luck,
Dave H.
96 855
93 854GLT