As the description says you need to train 15 researchers in any level. Note that you do not need to have 15 concurrent researchers, you simply need to train 15. So you can get this by replacing dead/fired researchers and therefore do not need to upgrade your spawn pool. You do need 750 tourmaline (375 with the "Enlistment" Production influence tech) which can be somewhat hard to find. Tourmaline is most common in the "dirt" (upper) levels and each block gives 20 (30 with the "Luck" Production influence tech) so you'll need 13-38 blocks to buy all the upgrades. Alternatively, you can dig straight down to the grey stone levels to find and sell dragonforce. You only need 40-80 dragonforce (3-8 blocks) to buy enough tourmaline to upgrade all your dwarves.