Upgrading from ESX 3.01 to ESXi 5.1

Hello all -

I just wanted to throw this out there to get an idea on how to accomplish what we are trying to do.  We are currently running ESX 3.01 in our environment.  We are currently planning on upgrading to ESXi 5.1 and as a part of this upgrade, we will be purchasing new hardware. 

My question is - once I get the new hardware in place and installed, when I power down my existing ESX 3.x vm's and copy them to my new hardware - what will I need to to make this work?  I know that the virtual hardware version needs to be upgraded (somehow??) and also the vmware tools need to be upgraded - for each of the machines.  Other than that, any tips, pointers or info that you can share would be greatly appreciated.

Thanks

sb