Which seal are you referring to? I'm using an upside down fridge, BTWDarren said:P&K,
Don't drill it at all. Just run the lines under the seal at the back. To gas up just open the lid and hit it with some co2. No need to gave the gas connected permanently.
Drill at yor own risk.
Had mine running with lines under the lid with no drilling for years now.
I know I need a drill, but what about sealing the hole, so the cold air doesn't escape?