Have oil leaking from corner of head gasket should I try a sealant .

There is no mechanic in a bottle that will permanently fix a blown out head gasket. In an emergency it's temporary at best and you will still have to do it properly when you get it home or a shop. Just think, a chemical goop circulating through you engine 'looking' for holes to plug. After the gasket is repaired all that crap must be flushed out, it will plug the oil holes in rod bearings, and more. Bottom line, no sealant.

Is it the valve cover gasket or the head gasket? if the latter, then take Mr. Nut's advice- tho I can't remember the last time I saw an oil leak from a head gasket-