I don't think that's a 1998 model at all. Back then, the design of tractors consisted more on square and straight lines. I'm leaning more towards 2005 or more.
You can try and check identification plate and see if there is any mention of the year. If not, then try searching for the one on the engine, usually in the valve cover as is should something about complying with the EPA emissions requirements of XXXX year.