Configure Microsoft NLB into already existing casarray

Hi

We have two exch2010Sp1 servers running CAS roles & are member of casarray.abc.com. These servers are also running HT roles as well.

Currently Casarray is configured with DNS round robin but without NLB. We want to introduce MSNLB on to this Casarray.

My questions are:

(1)Is it possible to introduce MS-NLB into existing Casarray, & if yes, are there any best practice guide available?

(2) If I have to rebuild new casarray, are there any best practice guide available.

Thanks.