Good day.

I bought a Lexus RX 300 jeep about three months ago from a known person. It has developed faults several times from oil leakage to horn and the likes. The one I'm currently facing now is changing the car from 4WD to 2WD. I drove it more than a week ago and discovered it was jerking and won't move without a loud noise from under the car as two heavy metals running on each other.
I could not drive it, had to tow it and placed it on neutral to avoid the noise and to aid smooth movement.
Now my mechanic said there are two solutions: either I buy another auxiliary, which he stated was the problem, or change to 2 Wheel Drive which involves removal of the auxiliary to avoid similar issues in the future.
I've attached to this post, the cost of everything I need as sent by the mechanic.
Please I need your advice on this.
Thanks