OK, first, the brake cylinders. In my experience, they have never slide back into their bores easily, and thats on many types of cars including the 850. Some people try to hammer them back in, but thats just asking for damage to the seals in the master cylinder. Here's the way I do it. Go to home depot and get one of the biggest C-clamps they sell. Make sure the master cylinder cap is off, take the C-clamp and put the screw side into the recess in the piston, and try to find a relatively flat spot on the back face of the caliper for the other side of the clamp to rest against. Then just gently tighten down on the clamp. It should ease the cylinder back into the bore nice and slowly, with no trauma. My old Datsun 280ZX you had to actually screw the pistons back into their bores, pressing straight in wouldn't do anything.

As for the squealing, are there any shims in place between the pads and the calipers? If not this is most likely the problem. Leaving the shims out (sometimes they rust or wear and fall out on their own) creates a whole lot of noise. They are there specifically to prevent brake noise. Also, when you put everything back together use some of that special anti ssqueal compound, which is like a high temp heavy grease. If that still doesn't cure it consider a switch to a different pad material.