I think your Safrane is fitted with the AD4 electronically controlled 4-speed auto trans.
I believe this is the same unit that was fitted to earlier Renault Lagunas.
When draining and refilling the transmission
, there is also a requirement to change the transmission fluid filter.
All of this seems to be covered in the Haynes manual for the Renault Laguna (book No. 3252). It may be advisable to obtain a copy, if only for the chapters relating to the automatic transmission.