Hello and welcome!
I see that your question has been up for an extended time without a response and while this vehicle is not in my area of greatest expertise I would like to try and help.
You may have an issue in the shifter, shift cable adjustment or interlock cable adjustment.
If you had trouble getting it into park when this first started then that's the first thing that needs to be investigated. The first thing I would recommend is removing the shift cable at the transmission (set the emergency brake and/or chock the wheels) and make sure it shifts into park ok by hand.
If so then reattach the shift cable and make sure it's adjusted correctly.
Then go back and see if you are able to shift it into and out of park correctly.
If so then retry the key and see if it will come out.
If it still wont' come out then the next thing to do would be check the interlock cable adjustment, which is the cable that goes between the shifter and ignition to prevent you from removing the key when the shifter isn't in park.
Well my brother took the car to a mechanic and I told him to check the transmission shift cable but the problem turned out to be interlock cable. Apparently a little white clip attached to a spring broke! They detached that cable and now the ignition can go all the way to the lock position.
By detaching the interlock cable, how will this affect how the car functions?
Unhooking the interlock cable is going to allow the shifter to move without the key turned on. Under normal operation you have to have the key turned on to be able to move the shifter from park, without the cable then it will move any time.
You'll also be able to turn off and remove the key without having to put the shifter in park.
Do I need to have the interlock cable replaced or I don't really need to?