The metal cans most certainly DO leak. Granted they will probably be just fine for at least a decade, but *every* 68k Mac I've dealt with that uses these has had them leaking all over. The tantalum caps trag sells are just fine, I bought the same type in bulk for my re-capping work.

Best way to remove the old capacitors is to do it cold as the heat from a soldering iron weakens the adhesive bonding the pad to the PCB and combined with the corroded solder it's very easy to damage the board. use some small diagonal cutters and for the larger caps grasp the can and gently bend it over, the leads will pull right out or come unsoldered. For the smaller size ones, cut them off as close to the base as you can. Either way you then clean up the pads with a soldering iron and solder the new caps in place. It takes just a few minutes unless you have a lot of corrosion damage to repair. Make sure you get the polarity right, tantalums like to blow up if you get them backwards.