Is Renault gearbox M017434 suitable to replace MO24550?

My megane coupe auto has been jumping down to 2nd with a thud. If I stop the car and restart it's ok again.
Renault Dealers charged £90 for diagnostics and then another £90 for further tests and then said it is the hydraulic distributor and need a new box (very expensive). I can get a used box MO17434 which has come out of a Scenic but the seller has asked me to cheque if this would replace mine which is MO24550. Can anyone help me please.