I suppose it depends on your experience and individual circumstances. I got my course book for the restricted category a few minutes after the class started. The instructor let me sneak in to fill an open seat, the beautiful man. I walked out with 96% on the written and 96% on the practical.
I brainfarted and picked that removing the firing pin is sufficient for transporting a restricted. It is not, also need to unload and use locks.
I also picked that the chamber of a revolver is in the cylinder, that's wrong.
On the practical I had some muzzle drift and jammed the test gun while handling it with my small hands and contorting myself to lock the slide back. It was a 1911, and I hadn't realized how large those would be to someone with baby hands like me. Was downright awkward, as my only handgun experience was using a smaller-framed glock that fit my hand quite a bit better and was quite a bit more simple to use.
So unless you're a complete stranger to firearms, then I think that studying the books and looking around for someone to let you get some hands on-experience. For the price of the course you could pay for some ammunition to use in someone else's gun if they'll allow it.
If you can find out the specific guns that you will be tested on I recommend looking around for opportunities to familiarize yourself with them, as most of the problems I saw in the class were from unfamiliarity and not any personal failings. I think I was in the low bracket of the class of 13 with my score of 96% of each, and none of us were particular experts. Stay calm, fingers away from the trigger, muzzle downrange at all times, and you should do fine.
Though, if this online course will give you peace of mind then go ahead but it doesn't really sound like anything that you couldn't learn by asking several shooters about it. Hopefully you'll have an instructor like mine, he allowed lots of time for questions and playing around with the guns.
I'd be happy to answer any particular questions you have.