Yes, firstly drain the sump you don't want to shatter a huge hole in it when full of oil. You can drain it with a tube as already stated via the dip stick hole (not on your BMW though... it has no dip stick!) just buy the proper vacuum tool! try the Chinese sites and they are well cheap and identical as they are all made there! Next buy a set of nut extractors you tap them on with a hammer and they tighten themselves...... remember though the sump plug is steel and the sump alloy so don't go smashing it on! Gently heat the sump area around the the plug trying not to heat the plug and then go for an undo!
You say it's siliconed.... do you know why, and what makes you think in might be glued' locked or whatever in place?
Impact driver ok if the plug is still patent but use a six point socket. but again drain the oil first! If the plug is to far gone then the nut extractor will work best.
