I think you will find these are led / smd and are soldered in place and are a pain to do they do not fail that often so check your wire connection's first and for dry joint's
the withe cover can get off. but i think it would be difficult. because the 4 white circles seems to be connected to the indicators inside the housing. so if i take theese off i am worried that i break them.
there is only one wire harness going in to the housing on the back and it seemes ok