IMHO you're worrying abøut the wrong end øƒ the sensor...getting the øld one out is often the worst problem.
Get a good six point box end wrench or deep socket and an 02 sensor wrench....use the six point or deep socket to break loose the old sensor (cut the wire off the sensor first).

Installing a new sensor is a piece of cake, just wrench it in to maybe 10-20 ft lbs...it's like a spark plug so don't screw it in there with all your might!

The least wiring hassle you can possibly have would be a genuine volvo part...exact replacement rght down to the connector. I suppose volvo could throw a curve at you with an updated connector (they've done it to me on other parts, like a neutral safety switch that I had to rewire the connector to the later service config) but prob not.

Keeping the same connector and pigtail you will probably get a better price from fcpgroton.com or somesuch vendor than the dealer.

But IMHO the best deal is a generic 02 sensor...all you do is strip the wires you cut off from the sensor and the wires from the new sensor, butt them and crimp them in the connectors provided with the generic kit, solder them (this is important), tape wrap with a high quality 3M or better electrical insulation tape, and install. You can get the generic sensors from RPR, or IPD, or just about any furrin car parts place...the only thing that matters is the thread and whether it's a heated sensor or not.