My 2002 Doblo is having problems getting into gear.

I've had a look and there is a ball and socket joint, from which, the ball has popped out. If you place the joint back together you can get it back into gear but it pops out after a few minutes driving. When it pops out the gear knob goes loose when you pull it up or down but it doesn't move up or down which stops me from putting it into gear.

Is it possible for me, a complete novice under the bonnet, to fix this? If so, what parts will I need? If you have any tips on how to do the job that would be great too!

If its not possible for me to fix it what should I expect to pay a mechanic?

Cheers