With ESXi, you won't have a Service Console to traverse to the vmfs volume of where your VMs .vmx file is located at, you could use the VI Client and the datastore browser to locate the .vmx file and download it to your local computer for modification and reupload, ensuring the VM is powered off when you update the configuration file. What type of video setting are you trying to make? Have you gone through the VM configuration to see if you can edit without having to go to .vmx file? If you're using vSphere, you actually have the option of editing the .vmx right in vSphere client which is very nice for adding entries without having to manually edit the file but if you're using 3.5, then you'll need to manually edit the file for any settings not exposed through the VI Client.
=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at:
VMware Code Central - Scripts/Sample code for Developers and Administrators
If you find this information useful, please award points for "correct" or "helpful".