1) Start with the cap suspended on something so the wax will drop off

2) Using a heat gun, melt off the outside wax and get it warm enough to be able to pull out the insides

3) This is how it will look.

4) Find a replacement cap that will fit inside. (the correct value of cap is always good)

5) Make sure the leads are going to be long enough, and that the splice is solid.

6) Stuff it in and use hot glue to seal the ends. Brown glue would be preferable.