How can i set REHLDS files to cureent HLDS without changing?

Not sure about REHLDS.

So, you have add REHLDS and everything is fine?

Sorry, I'm not sure. I have tried once. I end up destroyed my own server. LOL.

rehlds doesn't effect your gamemode. (if you do it correctly)

if u installed regamedll - nothing needs to do
if u intalled rehlds - u need to install reunion instead dproto (need hides this msg?)
if u installed reamxx or amx 183 u need to recompile all your plugins absolutely or will get crush sometimes
reapi - is a module with some nice availibility, not needs to install if u're plug don't will use it

dat's all i think
of course needs to check all new good cvars