Tejas,

I would hold off for a couple of weeks.  The next release is coming this month.  At that point you can update the SEPM server, then clients.  For updating the clients there are a variety of ways to upgrade them.  If you are using the SEPM for deployment it is pretty much straight forward. 

Open SEPM Console
Click on clients
Select the group you want to update
Click install packages
Click Add Client Install Package
Select the latest package at the time
Set your features for the upddate
provide the source (if other than the managment server)
set the schedule (if necessary).

Good luck.

Latest version of SEP is MR4 MP2

 Refer the document below for upgrading to latest version.

JUst to let you know, upgrading from MR3 to MR4 MP2 directly is not recomended.

Ideally it should from MR3 to MR4 and from MR4 to MR4 MP2

Migrating to MR4 

http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008121712452848

Migrating to MR4 MP2

http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2009051906042048