Corsa-B.uk - Vauxhall, Opel and Holden Corsa B Owners Club

my engine is loosing oil and water, but cant seem to find any leaks. i have been told this means my head gasket is gone? there is a little bit of mayo under the oil cap. how much? or how easy is a head gasket to do? i have a a 1l 3 cylinder engine. is there anything else that could cause this? i havent noticed it smoking and dont seem to have lost power, mind u it didnt really have any to start with haha

any help would be appreciated
Cheers