The FFG seems very daunting at first, but I just started playing DW a few days ago (Though I played SC for a long time before) and I have a very good grasp of the systems.
Actually you will be very thankful you have so much available to you on the ship, you're really able to do a lot. And you can sure make life difficult for submarines if you have 2 helos aboard, and if you have a P3 in the area you can be a real danger.
Make sure to learn how to use the towed array of the FFG and then learn TMA afterward. The mission "Seikan Tunnel" is an excellent way to learn all of the systems of the FFG, including CIWS and the SM2 missile, I was once shot at with a missile in the seikan tunnel mission
Learning the TA in the FFG is probably the most or second most important thing you can do. In the seikan tunnel mission you can learn about the various depths the towed array can be set to which will either drag the array on the ground, or put it at a deep enough level to get the best contact detection, etc. There are enough surface ships around to make it challenging. You'll have to learn to use your contact list in the sonar suite (look at the signal to noise ratio) to see which contacts are possubs and which are trawlers or other large ships. And you'll need to learn about the LOFAR (narrowband) to make sure you're not shooting the Harushio Japanese sub by accident, or a trawler. You'll also be given the opportunity to use your active sonar or high frequency sonar to detect and mark contacts in the water at close range.
The other thing you need to learn about is using the helo, but to be honest it's extremely simple, press F3, set green deck, click the "ship" link button and figure the rest out yourself.
Learning how to operate the GRAMS and deciding when it's best to use OTS buoys vs heli buoys is another important thing. A good mission for learning these is the spratley island resupply mission. That mission will also teach you about radar, SM2 and CIWS.