Speakers Not Working on 3DS XL

Firstly, my 3DS XL (New Edition) was already sent in for a repair when it wouldn’t boot after my friend had tried to mod it (Kinda stupid of me). When it came back they had it working again but said that its sound only works when it has a jack plugged in. So the speakers don’t work and I don’t know what could be the issue. Also it seems as though the 3D is constantly on and the slider doesn’t work. Have not opened it up since I don’t have the tools or knowledge yet to attempt to fix it. Any ideas on possible issues and solutions? I know it was attempted to be modded which can cause issues but still would love any feedback for helping to fix it.