Water box mod

[1100 stxer]

I have recently purchased a waterbox ( aftermarket ) and was wondering if any one had some advice on removing the stock one, and on installing the new one? It almost looks like there is not enough room to pull out the stock one but I might be wrong. Any info will be appreciated. I ride a '97 1100 stx this is the one with the battery under the seat, not in the hull.
Thanks in advance.