As for the drain plug, although I haven't had that specific problem, when I rounded the edges on my oil pan drain plug I used a pipe wrench to grip it.
Don't have knowledge about thread pitch. Don't toss the old one. Use it to compare to the replacement. Would try the pnp or as a last resort, the dealer. Certainly is more cost-effective than striping the threads on the housing with a wrong plug. Others will have more knowledge about your blower.