Yes. You have a couple more options. They make a self tapping over size drain plug just for this problem. The plug is bigger than the original and actually makes its own threads as it is installed. They also make a kit which is designed similar to the self tapping plug that once installed it never comes out it has a quick connect fitting on it that attaches to the plug to drain it so it doesn't have to be removed again. These are both after market options and would need to go to a parts store to obtain them.
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If the helicoil can't be removed I suggest an expandable plug. It is made of rubber with a bolt that goes through the center of it. As you tighten the bolt the plug expands and seals the hole. As far as the size It depends on how big they made it when doing the helicoil. It will either be the size of the original plug or one size bigger.
You just need to remove the lower. You probably know the procedure, but if not I will attach some information to help.
Unscrew and remove splash guard. Drain engine oil.