Brimmed tank is much safer than one with just fuel vapour in, they are the not so silent killers.
If you do try anything yourself, fill it with an inert gas like argon or CO2, but still be damn carefull, also make sure you support the tank 'cos once you have removed the bolts, the filler tube, wiring and fuel lines will get ripped right off as the tank drops on the ground!
The reason I know is because my tank fell on me instead!
Nowadays I cant believe I was that stupid OR that young!