Given that the alternative is landfill, use your heat gun (wife's hair dryer or oven) to remove the guts from the case and replace what is needed. IT may not be just that cap.

If you slide the potted guts out of the case, you then may freeze it hard, and hit it with a hammer to shatter the potting. This may help you get to the individual components faster. Been there. Done that.

Peter Wieck
Melrose Park, PA