I am the owner of a(n) 2002 jaguarxjr.
It will accasionaly pop into restricted mode. Or it will show the engine light.
After awhile they both turn off. Then at Random intervals turn back on.
What is my problem? Or what do you believe.

The next is I am wanting to change the console unit for the radio.
It's kind of old and outdated. Will it be difficult? Or will it be as simple as changing it out on a regular car.

 

ok an engine light will mean the car has stored a code(s), to read these codes and diagnose the issue you need a code reader, or to give it it's correct name an OBD II scanner, you can have the codes read at an Autozone store, or buy a cheap one and do the job yourself. You can pick them up online. Once you have them, you can post on here for a course of action to take to fix the issue.

Many threads on here about stereo upgrades, use the search function to see what routes you can take.

 

There is a current thread on a stereo faceplate just becoming available to replace the OEM with a single din aftermarket unit.