This isnt a totally bad thing. Its magnesium alloy i wouldnt try get it welded.
Its actually quite easy, take off wheels, un bolt all suspension arms, use jack to lower spring pan arms to take springs out, dissconnect brakes, take off exhaust and heat sheilds, unbolt 4 bolts to drop the subframe out, then put it all back together!!! At first when I did mine I was thinking a mechanic was goign to charge me an arm and a leg. Thank god I have a mate who works at BMWs so he did it for me with myself passing him the tools. If I were to do it again I would just go it myself its that easy!!! I bought the whole back end of a car all arms/subframe/brakes/brake lines/ cables etc etc etc, it was a good chance to replace my worn arms etc etc etc too! try think of it that way!!! hahaha... Good Luck!