You're doing it properly as you want to upgrade your vCenter first as it's the proper path, but note it'll need to run on 64bit going forward and a whole new dynamic with how to install since it incorporates SSO. Definitely read through he Upgrade KB on their site and review everything before jumping in.
VMWARE: http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=2021202&sliceId=1&docTypeID=DT_KB_1_1&dialogID=774384880&stateId=1 0 774412092
Regards, CSSMP