1999 GMC Savana 2500 Problems

AS I WAS ABOUT TO BACK OUT OF A PARKING SPACE AT A LOCAL MARKET, I PRESSED THE BRAKE PEDAL, AND IT PROMPTLY WENT TO THE FLOOR. FORTUNATELY I LIVE IN A RURAL AREA AND THE ROUTE HOME DID NOT REQUIRE MY DRIVING IN A HIGH SPEED/TRAFFIC ENVIRONMENT, BUT I NONETHELESS HAD TO BE EXTREMELY SLOW/CAREFUL TO GET IT HOME, AS I HAD MINIMAL BRAKING POWER(AT BEST). ONCE I GOT HOME I BEGAN TROUBLESHOOTING MYSELF INCLUDING CHECKING BRAKE FLUID LEVELS, ETC.(FYI, PROBABLY ONLY A FEW HUNDRED MILES ON VEHICLE SINCE BRAKES WERE DONE). WHILE CHECKING THE UNDERCARRIAGE FOR SIGNS OF LEAKAGE/OTHER THE FIRST THING THAT STRUCK ME WAS THE AMOUNT OF RUST ON THE FRAME/OTHER METAL PARTS. WHILE I UNDERSTAND THIS VEHICLE IS NOW APPROACHING 15 YEARS OLD IT HAS BEEN IN STORAGE MOST OF THAT TIME(SEE CURRENT MILEAGE)AND AS SUCH, HAS BEEN OUT OF THE ELEMENTS FOR THE MOST PART. THIS INCLUDES VERY LITTLE(IF ANY)DRIVING IN WINTER CONDITIONS(IN OTHER WORDS, ROAD SALT). QUITE FRANKLY I'VE SEEN VEHICLES PARKED OUT IN FIELDS FOR DECADES WITH LESS RUST. ANYWAY, WHILE TRACING THE BRAKE LINES FROM THE MASTER CYLINDER SURE ENOUGH I FOUND THE(FIRST??)LEAK. IT IS IN AN AREA LOCATED ON TOP OF THE FRAME WHERE 2(?)BRAKE LINES ARE FASTENED, JUST BEFORE THEY TURN INTO A (CONTROL MODULE?), WITH THE ACTUAL LOCATION BEING JUST BEYOND THE DRIVER-SIDE FRONT WHEEL WELL. LOOKING AT THE CURRENT CONDITION OF THE BRAKE LINES, FUEL LINES, GROUND STRAPS, ETC. I WOULD NOT TRUST ANY OF THESE TO LAST MUCH LONGER...LET ALONE THE FRAME ITSELF. IN CONCLUSION, THE THOUGHT OF THIS THING(OR OTHER SIMILAR CONDITION VEHICLES)OUT ON CROWDED OR HIGH-SPEED ROADWAYS, WELL, I'D CONSIDER THEM SERIOUS ACCIDENTS JUST WAITING TO HAPPEN...AND SPEAKING AS ONE WHO LIKES TO MAINTAIN HIS VEHICLES, I DO NOT SEE THIS AS AN OWNER PROBLEM, ESPECIALLY WHEN IT LOOKS AS THOUGH MANY HAVE SHARED SIMILAR(GM/CORROSION)ISSUES OVER THE LAST FEW YEARS, HERE AND ELSEWHERE. *TR