Schema update forest and domain

I have a network which is running a 2000 forest level and a 2003 domain level. There are two 2003 Domain controllers in place now. I would like to add a 2008R2 Domain controller into the domain and also keep the 2003 Domain Controllers in place but at lower roles. I will want the 2008R2 DC to take over the FSMO roles, and then over the course of time I would like to demote the 2003 DCs and go completely with a 2008R2 infrastructure. I have read that doing a schema update on the forest level to 2008 would be bad if I want to keep a 2003 DC in place in the domain... thus can someone give me an overall solution to accomplish this task, which is to do a Schema update to accomodate a 2008R2 DC (I have memever servers in place already), transfer the FSMO roles to the 2008R2 DC, then over time demote the 2003 DCs and introduce aother 2008R2 DC. I would also like to know if it is possible to do a schema update now to 2008R2 BEFORE adding in a 2008R2 domain controller? Say, for example, I wanted to put the 2008R2 DC in place next month, but I just want to prep the forest/domain for it now... what steps would I take to do this?

Thank you...I greatly appreciate it!