I did my MX3 lower ball joint myself in the back garden. ok, smaller car, but much less space to work. I used a rather long heavy metal pole, slotted it between the wishbone and chassis, and gave it a proper heave-ho and popped it. It can be tricky as it will try to pop back in unless you fully pop it out. Loosen the balljoint nut too infact, remove it as you dont want to damage it (this is the nut that tightens up the clamp that the top of the balljoint sits in), I may even have prised the clamp open a touch.
definately a DIY job though, just make 100% sure the car is stable and well supported, because you are really going to heave that joint off (my MX3 wobbled somewhat, quite unnerving)
once out, replace the joint and re position into the hub, when I did my mx3, at this point, I removed one of the hub retaining bolts to allow a bit of movement-this made it a heck of a lot easier re fitting the new joint.
good luck!