vCenter Upgrade from 4.1 to 5.5

Hi,

I am relatively new to virtualization and hence seeking basic help. We have a vSphere 4.1 system installed at customer site. All hosts are on ESXi 4.1 and vCenter 4.1  is on one of the VMs on one of the hosts. We will be adding five new hosts with ESXi 5.5. Since vCenter 4.1 does not support ESXi 5.5, we will be upgrading vCenter to 5.5. I have following questions:

1. Since existing vCenter 4.1 is on host with ESXi 4.1, will there be any problem in upgrading vCenter to 5.5?

2. Will the upgraded vCenter 5.5 support ESXi 4.1 hosts?

3. Is there any documented procedure for step-by-step upgrade of vCenter Server?

4. Any other recommendation?

Thank you

Regards,

coepengineer