A tall tub dishwasher should fit in your current appliance opening.
As long as the external measures are the same, you should be able to seamlessly replace your current dishwasher with a tall tub model. In a tall tub dishwasher, the model is redesigned to have a larger interior capacity while generally leaving the outside the same dimensions.
Of course, different dishwasher models have different dimensions so you should always measure your opening carefully as well as the dishwasher you are looking at prior to purchase.
“Whirlpool Undercounter Model Product Dimensions Guide.” Us-appliance.com. N.p., n.d. Web. 4 Dec. 2011. <site.us-appliance.com/pdfs/FRREJGWMSWLU.PDF>.