2003 Lincoln Navigator QUESTION

I HAVE A FRIEND THAT IS A MECHANIC THAT WORKS OUT OF HIS HOUSE AND ALWAYS DOES MY WORK ON MY CARS FOR ME. HAVE ALWAYS BEEN HAPPY WITH WORK AND PRICE. I TOOK IN MY WIFES CAR BECAUSE THE A/C FOR THE BACK SEAT IS BLOWING OUT HOT AIR. I TOOK IT IN AND THERE IS SOME LEAKS HE IS TELLING ME AND IS GOING TO REPLACE MOST OF THE PARTS THE AIR FLOWS THROUGH. HE PUT IN FREON BUT SAYS IT WILL LEAK OUT IN A MATTER OF TIME. IT IS GOING TO COST $530.00 TO REPAIR. I DID CALL THE DEALERSHIP AND THEY SAID IT SOUNDS LIKE THE WORK THAT NEEDS TO BE DONE COULD COST $1000.00 TO $2000.00 DOLLARS. IS THIS THE RIGHT THING TO DO.