ok. time for a tune up. do your spark plugs and spark plug wires if you havent already. also replace your fuel filter. all easy cheap stuff. the screeching of the brakes i wouldnt worry about too much unless you've had your brakes on there for a while. the shaking could be that your rotors are warpped and you might need to get them turned. your caliper piston will always have to be compressed when you replace your brakes. if you have to use all of your strength to get that piston in, then something is wrong with your caliper. if it went in easy and smooth ur fine.
