If it does not leaking you can just use topsider
for oil changes. When loosening a oil plug allways use a 6 point wrench or socket.
And...If if you really want it off....
If you cannot get it loose with vice grips, then
another alternative is to weld a short bolt on
plug so you can have something to put a wrench
on. If you are not up to this then I suggest
you take it in and have it done.