Barry's pretty much covered the waterfront on it, kat.

If you are planning on somehow living there while all this is going on, if you can possibly, by any stretch avoid it, do so. An addition or renovation can sometimes put a lot of pressure on relationships and while it can be interesting and informative, its really not worth the added stress if you can possibly avoid it.

Remember too that sometimes a wish list can cost a lot more than we hope it will, so be prepared to compromise on a few goodies in favour of good construction.