I've never had to replace mine. I do spray it with electric contact cleaner spray regularly (~ every 2 years).
Cheapest one I could find in a 30 second search: € 13,77 incl. shipping - for 406 2.0 HDi & 2.2 HDi.
Maybe not, looks like both are indeed the same: both OEM numbers are listed at the part shown here: https://www.ebay.co.uk/p/Sensor-Throttl ... 3017021256 .
Mine has now 627 k kms (390 k miles) and has never needed a new head gasket.