On most Sonics, the radio is also the control panel for settings like the chimes, rear wiper operation, and other options.
Unless it is not working, I would not change the radio/CD player. Then, I'd get a used one that was unlocked from the VIN, which may still need to be programmed to the vehicle after install.
Steering wheel control integration into an aftermarket stereo can be done with either a PAC SWI-RC (about $29 on Amazon at the moment) or a Metra Axxess ASWC-1 (about $53 on Amazon at the moment).
The Metra is supposed to be easier to install because it "auto-detects" a lot of settings while the PAC requires that you set DIP switches to configure it to match the car + aftermarket radio, but personally I don't have any issues reading instructions and I'm a cheapskate so I went with the cheaper PAC unit.
As for aftermarket head-units - anything double-din will work. If you get the Metra dash/install kit it'll include a unit that retains the chimes and such. My main reason for replacing my stock unit was my 2012 had a bog standard CD player with no screen - I wanted Android Auto for navigation as well as a backup camera. I don't miss the stock stereo one bit.
The ONLY thing I found aggravating was that the aftermarket stereo didn't interface with the built-in microphone in the vehicle (wherever that is - I assume there's one somewhere since it had bluetooth). I ended up clipping an aftermarket mic on the headliner and then running the cable behind the a-pillar and through the dash back to the radio. The cable is well hidden but the microphone itself certainly doesn't look OEM clipped up there . . .