Yes I agree with you @db4690 . I made a big mistake when I purchased my early 70’s Ford truck by not purchasing the service manual. It was listed in the owners manual with a coupon to buy it, only $6!!! What a bone-head move on my part. My only defense, at the time, my only diy car-work inclination was oil changes and tune ups.
But for the OP, here’s another idea, OP might still be able to purchase the factory service manual. Don’t recall exactly how I discovered this, but recently I found out it’s still possible to purchase the factory service manual for my Ford truck. They had the original owner’s manual too. I think they only had the FSM in CD format though, so you’d read it on your computer. It wasn’t overly expensive, $20 or so.