Depending on what you are calling 'frozen,' I would not take a large pipe wrench to that plug. But, if it is just 'stuck-in-there/been-there-awhile' frozen I would get it out as opposed to drilling another hole. Spray it down with penetrant (blaster, Kroil, et cetera) and let it sit for a while (period of time long enough for the oil to work).
Get the appropriate-sized wrench on the plug, turn a degree or two to tighten the plug first, & then see if it will back on out.
Brad
