its easy , 4 bolts hold it on 16mm . you will need 2 hand brake cables (£50) the ABS sensors plug straight in to the old ones as do the brake pipes.
did this conversion a few months back took me an hour to do whole rear beam was £200 from matt blacks place, although i went a chose a good one as some times parts from there are broken ie the abs sensors just choped off , as matt says it all depends on who is breaking it.
with the ABS if you switch it off the brakes will become unbias'd as the bosch abs pump distributes the bias you will need to get some sort of bias valve in there as a clio with no ABS and unbias's brakes is scarey trust me i have experienced it