My feeling is that gorillas are pretty important just because they are apes (for practical research purposes, although I think they have a fair degree of intrinsic value too). Seed dispersion seems the least of these benefits. (On the other hand, I suppose the existence of other apes poses a disease threat to humans).

We should really demand more funding for research, in general. Under-funding research may be the single most irrational thing we do as a society, considering the return on investment.