my right rear strut is bad if i get coilovers will i still need to get new struts

 

If you get sleeve over - coil overs such as ground controls,skunk2,omni, then yes.
If you get full coil-overs then no because they are built as one unit, normally these are a little more expensive but will bring a greater result. (tein basics,omni full coil-overs, progress, buddy club n+,d2,aPEXi,and so on!!!!