Hi Rob,
Would agree with other postings.
1. You need to prune out the dead / disease wood.
Remember to clean your seceters afterwards, just wipe over with
methylated spirits.
2. Burn trimmings
3. As insurance, paint the cut surface with a fungicidal wound paint -
like Medo or arbrex
4. Remove fruit - certainly for first year, thin in 2nd and should be
ok from there, unless particully heavy cropping.

Plums generally don't get prunned owing to silverleaf disease.