They will fit just fine as there is no difference between a 99 and 02 wrangler. As for when you need new wheels, not sure if you mean when you would need new tires, or if you mean the wheels themselves.
+1
Like she said, there is no difference. Well, there's a slight difference in size between the regular tires and the optional BUT they are all interchangeable between the models. Wheels and tires.
As for price, you'll have to look and see how much the exact tires cost retail and figure out how much they're worth to you. Personally, I'd look at other tires out there since the stock Goodyear Wrangler AT's aren't that great.