Re: Idiots question about relays....
they can vary, depends what they are designed to switch so although there are a few generic types, they look the same but are actually different internally, you need to get the right type, you may find a suitable one on a eg a Ford so almost any scrap yard will do.
The lambda, first, get a Bosch one, does not like other makes much, and these universal types are a waste of time and money, do the job once and fit a Bosch. The job is best done by jacking the front up, then disconnecting at the joint on the bulkhead, tying 4 foot of string on the connector and the other end onto eg the wiper arm, go under the car, unscrew from exhaust with big spanner (22mm IIRC) and pull the connecting wire and string down. Bolt up new lambda, tie string onto new wire, go back to the wiper arm and pull string back up through the back of the engine, then reconnect, and refit to bulkhead.
There may be the odd clip to get at at the rear of the engine, but it is a real pain to thread that wire back up the back of the engine without the string to help it along.