You already have the general idea of how to keep fish, cycling, maintenance, cost, and general knowledge. ... Now, multiply all of that by 10, and cost by about 20.
You will have to re-research saltwater fish and see what is compatible. Do you want to keep
FOWLR (fish only with live rock)? Or do you eventually want a reef tank with corals and clams? There are some fish (especially really colorful ones) that aren't compatible with reef systems because they eat the corals.
Once you answer these questions you can decide what temperment of fish. I kinda would compare damsels to cichlids, and clowfish to guppies. They have completely different attitudes, and can't be together.
For
FOWLR, you can get away with standard lighting used in
FW tanks, since live rock doesn't need metal halide lighting or 8 T5s. I ran my tank with 2 clowns and a blennie with live rock for a few months under the stock lighting that came with the tank. Of course if you upgrade lighting you will see more life from the
LR and be able to keep corals.
There are more parameters to watch out for. It's not just ammonia, pH, nitrates/
ites. Salinity and phosphates also play an important role in
SW keeping (and even more when adding corals).
As for weekly maintenance, you'll still have to do
PWC and testing; but to get pristine water you'll need to get an
RO/
DI filter and mix that with salt.
Take a look at my thread (link in my signature) and you'll see everything I did to start from scratch. My tank was empty and I went to the
LFS for just some ideas and help; but I walked out with $300 of sand,
LR, salt, etc. I explain what I did to start off and kept a decent log.
Good luck! If you take anything from this post, please let it be this: "It'll cost ya, but if you love it, and take care of it, it's totally worth it"