I do understand where garage is coming from, for two reasons, one if the parts are wrong they have a delay with ramp blocked whereas if their supplier provides the parts , the parts company sends out on next van. The other is there is a profit element on the trade price of parts.

Unlikely to be counter thread, just tight.
Don't take this as gospel , but I did some cross referencing on the belt and it seems to be a PAS XU10J2 Peugeot Citroen 2.0 litre engine.
I found this for the Peugeot variant of the XU10J2 , it lists many of the RF* numbers but as this book only goes up to 1996 that may be why it doesn't show the RFW. Apparently the engine was also used in Citroen Relay versions , but not in my books.
The book mention diesel timing but I think this is a misprint as no sign of an injector pump.
See if these instructions bare any relevance to yours. Your risk obviously