Best-selling author, perhaps on a publicity tour, Pope John Paul II is making news again, giving a papal nod togenetic engineering-- albeit with some heavy moral guidelines. The 74-year-old Pontiff today told members of the Pontifical Academy of Science, a Vatican advisory group, that gene research could mean "sick people who cannot be cared for adequately now . . . will be able to benefit from necessary treatments that will improve their condition or even cure them.'' The Church first signaled the attitude change in last November's revised Catholic catechism; the taboo on engineering super-people -- even longer-living popes -- remains in force.