We just recently purchased a new house and the appliances were left in the home...there is a Sharpe Carousel II Convection/Microwave oven here. The Manufacture date is November 1990. I can not figure out how to use the darn thing and there is no user guide. The number buttons 1-5 work when they want to so I have to keep pressing the minute plus button for everything. PLEASE HELP!! Should I just buy a new one instead?? I work at Walmart and do not see one that says convection on it.