coil overs

hey all,
ok, i need new struts and springs for my 92 escort gt. I see these sets of coil overs on ebay for like $50 and that is way cheaper then replacing the struts and springs. I heard that coil overs replace the strut and spring. Is that true. Is it worth buying the coil overs. If i do buy them, do i need any specific parts. As you can tell, I know nothing about coil overs, any help you could provide would be greatly appreciated. Thanx.

I was going to put coil overs on my 91 LX. I was in the same deal you're in and it sounds sweet. My friend who is a mechanic also teaches an auto mechanics course told me this: Coilovers are great but keep messing up your tire alignment. So I look at it this way. I guess coilovers are good except for the face of paying every month for an alignment or buying new tires every 6 months because they wear funny.