This place
has a really good website about reserve studies including a nice example study. Disclaimer: I have no affiliation with them. My HOA has never dealt with them. I don't even think they operate in Florida.
One thing an outside Reserve Study will do for you is tell you things you probably don't want to hear. Preparing an in-house pseudo-study won't do that because often a board of directors will pre-determine the outcome it wants to see ("Yeah, don't include the pool in there."). I've been advocating for my HOA in Florida, where reserve studies are not mandatory, to get an outside independent Reserve Study done for 4 years. No luck so far.
With a reserve study such as the sample one above, I think the majority of associations will be lucky to have one or two board members who can even begin to comprehend it. I'd say "vast majority" but my sample size is too small to make that generaliztion. Last year I had a few color copies of the above sample reserve study printed and passed them around to directors and members of our Finance Committee. I said, "Imagine if we had something like this tailored for our community!" I received no feedback from any of them. Zero.