Even if you bought your sensor at the dealership at retail prices, it would run less than $160USD, leaving $240 for labor. Given that it is really a 30 minute job, that is allowing the shop 3 hours @ $80/hr. You can get Bosch sensors at places like Autozone for under $40 that will work just fine. I put my 240 up on ramps and had the new sensor in place in minutes. Trace the wires back from the engine compartment. Two white wires with a clip connector and one black or green wire with a rubber bullet connector near the passenger side firewall in the engine compartment.

The overdrive relay is available everywhere online for about $25, and it is easy to get to (to the left of the glovebox in the center console. You just disconnect the old one and connect the new one. To pay $175 in labor for this 20 minute job (including clean-up and digging for the last cold beer at the back of the fridge when you are done) seems non-sensical to me.

Spending $600 on a car worth $2000 is a large fraction of the value of the car! Old Volvos are good value-- they become great value when you start doing the simple stuff yourself and hanging onto your hard-earned cash.

Good luck!

P.S. This is also a good opportunity to pick up a few tools with some of the money you saved-- i.e. ramps, a decent socket set, an inexpensive voltmeter...
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Herb Goltz, Aurora, Ontario, Canada '92 245 w/130K mi, '92 945T w/200K mi