How to fix my Volvo s40 stereo?

I made a dumb mistake and let my friend try to swap the stock stereo out of my 2000 Volvo S40 1.9T, because the stereo said "error" or something like that when I got it used. Instead of taking it back to the dealer like I should have, he snipped the wires connecting the stereo in, thinking he could just connect the wires to the stereo in his Acura, later in his Honda. Right now, it's a bunch of snipped multi colored wires in the cavity where the stereo was. How can I fix it and how much do you think it would cost?

If the old stereo had a plastic connector on it, then get that back from your stupid friend. If there's enough wire left sticking out of it, you could carefully splice each wire back together.

If there wasn't a connector, he threw it away, or it is otherwise unusable, go online or call a Volvo parts distributor (even a dealership), give them the year and model of car and type of stereo that was removed, and then see if you can get the connector or the complete wiring kit for it. Alternately you could see if you can find one in a junk yard. I don't know if the Volvo had more than one factory stereo option or if the harness would be the same for all of them. It might be. Another option would be to find a direct drop-in replacement stereo (or the same onne out of a junk yard), or one that would require minimum modification of the console to install. If it comes with, or you can order a connector kit for it, then you could splice that onto the old wire bundle.

To replace the harness, or just splice a new connector onto the old wires, you'll probably have to dismantle the console. If this is beyond your knowledge and ability, as I suspect it might be, take your car somewhere to get it done for you, preferrably someone who specializes in Volvo's or an audio installation shop who has a technician familiar with them. It probably won't be inexpensive. DON'T let your "friend" touch it again but DO ask him to help pay for the repair because he is an IDIOT. You are also an idiot, as you admitted already, for letting him do it.

That's wonderful. Can you reconnect the wires to the plug? If they're cut too short, try a bone yard or Ebay for a used plug.
You don't have to go to the dealer to fix this, although you can. Try some radio and/or alarm shops in your area, and tell them what happened. It shouldn't cost too too much.
There are adapters made for most stock radio's so no wires need to be cut.