Alex,
This is real easy.
The Sierra conversion is nothing new and not an engineering challenge in itself. Regardless the conversion does make the C500/501/550/551 type into a spectacular performer especially when fitted with the long range wing fuel tank (The fuel tank mod used to belong to Robertson STOL - which Sierra bought)
Any C500 series workshop should be able to look after your conversion, there is nothing tricky or difficult about the Williams engine and the conversion.
I have 1000+ on the type and engineering experience as well.
Enjoy !!!