2003 Other Jaguar Models GEARBOX FAULT CODE

MY CAR HAS A KICK TO IT WHEN YOU APPLY BRAKES LIKE IT WANTS TO KEEP GOING. WHEN IT TRIES TO CHANGE GEARS IT WILL SNATCH INTO GEAR LIKE IT SUDDENLY POPS INTO GEAR. SOMETIMES IT WILL NOT CHANGE GEARS, YOU HAVE TO CUT THE ENGINE OFF SO THE COMPUTER WILL RESET ITSELF. HOW EXPENSIVE IS IT TO REPAIR THIS PROBLEM? DO YOU HAVE TO REPLACE THE TRANSMISION OR WHAT WILL CORRECT THE GEAR CHANGING PROBLEM?