I am planning on replacing the roof on my 50-year-old bungalow soon and decided it would be a good time to put in some new insulation in the attic as well. The insulation there is the old loose grey kind. I suppose that I'll have to pull it all out first so that there's a place to put the new insulation between the boards. Some of it has gotten wet in places anyway and probably isn't doing much good. a) what is the easiest way to remove the old insulation? do I have to pick it all up by hand and bag it? The second problem is that there's no ventilation in parts of the attic. The second floor of the house is broken up so that there are 5 separate sections of attic that aren't connected. The crawlspace along the top ridge possibly has some ventilation through the gables (at least it looks like this from the outside, but I have no way of getting inside). The other 4 are on the corners of the building (the living area forms a T in the center of the upstairs) and, although I can see daylight breaking through cracks in places, there is no formal ventilation. I've read about the importance of ventilation, but it seems weird that the house has gone this long without any. b)Is there any damage I should look for? How important is it for me to add ventilation now, and what exactly is needed?

I am from Mississauga, Ontario, Canada. Would someone be able to just give a rough estimate (I know it varies a lot, but I am just looking for a range of the cost) on how much I am looking into if I want to take out a separate entrance for my basement apartment. Learner2