What model radio? Most Volvo stock radios of the same vintage and size (din-sized, versus double-din size) should be plug-n-play, if you get the security codes. E.G, if you have a single-din size and either have, or want to add, a cd changer, the CR 814 is a good bet.
Call around the auto salvage yards near you to see who has
volvo radios, from what years, and with codes (or at least with the vin number of the car from which they came, so you can see if the volvo dealer will get you the codes).
When you pull your present radio out, take a look at the plug or pigtail which connects it to the vehicle harness. Generally, in late '88 through '92, the harness connector will be an offset rectangular 14-pin item; however, some still were using the pre-'89 9-pin connector plus miscellaneous wiring. Know what you're looking for, so when you go to the junkyard you can see that what you're getting is indeed a direct plug-in.
If it turns out that you also have an external amp connected to your present radio, the CR 814 amp socket will accept that connector without modification.
No tools involved if all goes right.
Post further if you need more help as things develop.
Also use the search function re general topics on radio R & R, or model-specific inquiries.
For ideas on price range, check ebay motors, car & truck parts, electronic and audio; also check the classifieds here on the brickboard, where you are more likely to get knowledgeable and honest descriptions of what's for sale. I've seen plenty of CR 814s going in the $20-30 range on ebay, but often with outrageous "shipping and handling" tacked on-check all the details before you bid.
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We have met the enemy and they is us. [Pogo] S70 T5 cop car : Rough Rider suspension, Walmart fog lights, eBay speakers, ambiance by Pall Mall, trim by Le Duc d'Tape, 8-channel THD by OEM amps