As above (post was edited with budget after peg replied), just pick from a name brand (Sony, Pioneer, Alpine) so you don't hear about it later. Call up car audio stores, find out how much to install (including patching the steering wheel controls and hooking up reverse camera if it has one), and work back from there. I'd guess install would be $200-ish, maybe $250, so you could look at $650 head units.
Check these out…
https://www.joyingauto.com/au-warehouse/2-din.html
Had one in my car for 6 yrs and it is brilliant.
It makes the JBL H/U upgrade ($800) in our new 2nd car look like junk.
They ask you to give exact details of your car and supply the correct wiring loom for it. It is simple to install.
Plenty of "how to's" on YouTube.
These are fine, but I am much happier with a proper brand-name Android Auto head unit of a similar price (the Sony XAV-AX100 is what I got).
The AA interface is much more geared towards non-distracting use in the car, whereas the Joying HUs are basically Android tablets with a slightly customised interface, but overall it's still just a tablet.
That's not to say that they're bad. They're pretty good. The niggling issues I had with them (e.g. LONG boot time, app audio cutting out occasionally requiring a hard reset, poor AM/FM radio selectivity, app landscape display problems) just mean that I'd still pick a name brand AA head unit over them.
That’s a healthy budget. Should get a brand name unit for that much.
If getting a brand name unit with android auto or apple CarPlay just double check wether the phone needs to be connected by cable or will do wireless. The unit I got for my wife’s car was a lower end model and must be connected by cable. Slightly annoying, but it works so much better than the cheap Chinese units we’d had previously.
Could be for some. For us it works fine as is. 90% of the time we listen to radio and the phone Bluetooth connection for calls works really well. If needed for Navigation just plug it in.
Thanks everyone for your help and valuable advice.
He ended up getting one from Autobarn.
Any double DIN unit that support Apple CarPlay or Android Auto and use the navigation app from his phone. Need a budget though. Could recommend something that ends up being 50% the replacement cost of the whole car.