Mandatory reading for planning an upgrade (all for target version):
A) Upgrade and migration guide
B) Release notes
C) RN/README from OVA
D) Compatibility matrix (might be an individual document, might be included in the above)
E) Virtualization wiki for HW/ESXi compatibility
If there are move servers involved in the upgrade, you'll have to go through the above for each product.
Once you've gone through the above, you'll have all the required information to plan and perform a CUCM + IM&P upgrade