you are absolutely not too big, far from it. i've seen guys much bigger than you on road bikes and cross bikes and not one of them has looked like an idiot.
as far as comfort, you'll be leaning more forward. you'll probably move your body less over the bike and you'll have more places to put your hands. this is more comfortable for some rides, less comfortable for others. but for most rides with a smooth surface, i think you'll find you're quite comfortable as long as the bike fits you.
i always recommend trying a test ride before committing money, but your shop will probably ask for a deposit. if they do, ask if you can put that money towards another bike from them if the tricross doesn't suit you. take it for a nice long test ride and if you like it then you can buy it and dial in the fit perfectly.