check first to see if it's just the boot that's split, or if the ball joint is actually worn as well....
If the joint is still ok and it's just the boot, go to the motor factors and buy the cheapest balljoint they've got with a boot of similar size (IIRC i used a mk2 Cavalier one) and just use the boot - it will be way cheaper than the arm, and won't all need to be taken off to do