Front strut assembly

Hello, any help would be appreciated.
I had a 1998 Buick Park Avenue Ultra that crapped
out on me. Before this though I bought new rotors
and new brake pads. I also bought the front strut
assemblys new. I put probably around 1000 miles
on them before the car died on me.
After that I bought a 2005 Buick LeSabre. I
switched the rotors, brake pads, and calipers over
to this car from the park avenue. The reason I
changed the calipers too was because the rotors
and brake pads were too big for the original
calipers the LeSabre had.
Now, I want to know if this was a bad idea, if I
should change them back, and what type of
damage this could cause on the car.
I also want to know if the strut assemblys would fit
the LeSabre since again the only have like 1000
miles of wear on them and I think it would be a
waste of some perfectly good stuff assemblys,
specially since they cost me roughly around 180 or
200 each.
Does changing parts like this damage the car,
please help, I'm new to fixing my car's and would
really appreciate any advice or help you can give
me.
Thank you