Can I use de Sylinkreplacer with Managed Clients

yes you can use it. if not working then try sylink droper.

Yes you can. Are you using MR3 or later? Did Symantec Support provide the tool to you?

Sylink Replacer may not work in a workgroup environment, if your computers are in a workgroup use Sylink Drop.

Yes they sent to me the sylinkreplacer, and I'm using the latest version of the SEP, I will try to use de sylink droper, do the sylink droper replace the sylink communication to many clients at once???

Nope, Sylink drop must be run on the individual clients locally.

What u guys would suggest i need to change the communication on 40 clients, and let's say that would like to replace on all machines at once?

 Either use Sylink Replacer if that is not working..make sure you have picked the correct sylink.xml

if still not working follow this
http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008052008163148