I probably wouldn't put much money towards that bike. Usually the bigger the number for Fuji the lower end the bike with the first number being the frame and the second number being parts designation but they did some 3.0s which were at the bottom of the bottom generally. Anytime you see Tourney on a bike, either don't buy it or if you own it don't put much money towards it. Save that money for a better bike that suits your needs. Tourney is at the absolute bottom of Shimano's range though they do a spectrum in the Tourney stuff but at the end you really aren't getting marked improvements to the point you have quality from that line just slightly more modernized looks but the same not so good performance. Get the bike running safely with minimal money put towards it and save the money for something better. If it were a rare or high end frame that someone had inadvertently stuck some cheap parts on, yeah put a little towards it but these were a dime a dozen and nothing special plenty of other hybrids out there.

In terms of adjusting a derailleur you will need a standard JIS/CrossTip Screwdriver, this being my top choice but Vessel also makes some decent ones. Then for putting it on you just need a set of hex wrenches (Metric for most bikes from the 80s on), PB Swiss, Wera, Wiha, Silca are all excellent options but Bondhus makes decent stuff if you are looking to save a little but basic tools like hex wrenches are not a place to save money. Any tool you are using with some regularity and especially one that you would use all the time you want the best quality you can get so you aren't stripping out bolts and causing issues. Yes a lot of Ikea furniture comes with hex wrenches but it is a disposable item for cheap furniture not something you want to use on a bike or anything else but that. Only a rich person has time and money for cheap tools and if you don't want to invest in tools then support your local shop who can do whatever work you need (generally) you are paying not only for their tools, but their time, their knowledge/expertise and also to not have to do it yourself which takes time and time is money.