Here is the video guide for the Roco Air piggy back shocks. The TST and the RC are the same shock units with the exception of the mechanical TST valve vs. the shimmed compression valve in the RC, they are interchangeable so you can convert between the two.
The service is complex so if you are in any doubt please send your shock to a specialist.
The seal kit is Y8501251/P and costs £59.95
