87 Rear Coil Springs

I have an 87 linc TC with factory coil springs.. They need to be replaced because the rear of my car sags bigtime...for some reason i thought it was the shocks so i had them replaced... It still sags..:banghead: So i ordered brand new rear coil springs from NAPA..:rofl: My question is how easy are they to install and what tools would i need??? Or an online manual would be great....
Thanks