Or you could just ask me Dave... considering I converted it and have a copy of the invoice lol ;-)
Vapour filter https://www.lpgshop.co.uk/lpg-filter-y-inlet-1x12mm-outlet-2x12mm/
But I didn't specify which (exact) Valtek Liquid filter I fitted on the invoice... and I occasionally (rarely though) list Valtek filter solenoids on invoices when I've really fitted an OMB filter solenoid or similar. On the shiny cap bit of the filter solenoid it should say what type it is.. (a number after Valtek like 07). Probably this one https://www.lpgshop.co.uk/valtek-zavoli-emma-gas-lpg-filter-paper/
Just change the filters and leak check as Gilbert said. If cars come here for service I'll do a bit more like checking fuel trims, compare trims on different banks, connect to the LPG ECU with the laptop and check pressure etc... But that won't be necessary at all, wouldn't expect to find any issues if I converted it lol ;-) Usually when I get cars in for service converted elsewhere there's loads to do with calibration etc.