that does not make sense- provided your equipment has scart (or round phono-rca) sockets, you can connect it up. you should not need to replace anything. the easiest way is to connect the vcr and the dvd with a scart cable each, to the tv. usually, switching either device on (or pressing play) will switch the tv onto the right channel.
if you want to record on the vcr (from standard tv broadcasts) you need to plug the aerial into the vcr then, using another coax cable, the vcr's rf out to the tv aerial input.
post back if none of that makes sense and i will explain more!