No draining required to remove valve covers, willneed to remove upper intake though. And if the OEM gaskets are still on the valve covers you won't even need to scrape the gaskets. The OEM unit is a rubber bonded to a steel shim, and if it they are still in good condition may be re-used. If they are not OEM type then just make sure you scrape the gasket material away from the inside of the heads to keep from getting it in the engine.
If you do need to scrape gasket material, it is a good idea to do an oil change afterwards just to ensure any loose bits of gasket that may have gotten in the engine get cleared out.
You will know if the VC gaskets are OEM ones if they look like a O-ring bonded to a sheet metal shim.
Also, I would suggest that if you do need to replace the gaskets, use the OEM type (available from Ford dealer or FRPP only). They rarely leak, and are easy to install as they require no sealer and you can just tighten the VC bolts down, unlike normal VC gaskets that can easily be over-torqued.
When re-installing the upper intake, replace the gasket and follow the manual for torque specs/order- it is fairly important.