The specific reason why timing belt has to come off is because the tensioner idler pulley/bracket assembly is blocking one of the water pump bolts, possibly 2. You HAVE to remove the timing belt. If I were you, Id do it right with all OEM parts (belt, tensioner, idler pulley, tensioner pulley) and you should use an OEM water pump but if you wanted to save $150 bucks, go with a Gates water pump. The quality on those pumps is very good. DO NOT use any other water pump.
The balance shaft belt does not have to come off to do this job although if you have one, id replace it with new OEM stuff with a new pulley. You should get the timing belt tools to do this job (teeth spacer and tensioner pulley tool with 2 dots) The pin on the tensioner should be set so you can put it in and out after you set tension. Use a little rtv or red tack spray on the water pump gasket and use a new Oring on the water pump crossover pipe. If you retain the balance shafts, dont forget to make sure the rear shaft is in phase with the front. Its a really easy process just keep turning it until it balances itself on the pointer (there are 3 positions it will balance itself in) then put the front shaft on the pointer and youre good to go!