In no way should replacement cost $800. If your car handles well, stays is a realitive straight with your hands off the wheel on a level highway, tires show no unusual wear, it does not pull to the right or left when driving, I would not worry; however, if you are concerned, take it to a tire dealer's shop, and tell them what Volvo Serviceman said and ask for a check. Cost should be very reasonabe, less then $65 if relignment is needed. If,in fact, there is a problem with control arms, they could replace them for a fraction of what Volvo serviceman quotes. It cost my wife close to $200 for oil and filter change at the Volvo dealers shop using synthetic oil. The next time I did it myself for about $40.
wife close to $200 for an oil and filter change using synthetic oil. The next time , I did it forless than $40.