Soliciting Tips for New Aquarium

I just had the fortune to be given a 55gal aquarium, stand, UGF plates and
two working powerheads for free.

I would like to try setting up a nice tank for live plants. Since I need a
hood does anybody have any suggestions on if I should build one or buy one
and how many watts of light I'll need to supply? Do I need a timer for them?

What's the best way to supply CO2 and is it really that important?

Are there any good places to order plants from? My local PetCo says they
can't order anything special and they can't tell me the names of what they
do have most of the time.

What about substrate?

Also, if I tested the tap water would that help anybody making suggestions
on fish or plants?

Finally, I have been able to gather that the UGF I got with the tanks won't
be getting used so is there any other use for the powerheads?

Sorry for all the questions, I've never been able keep anything but Amazon
Swords alive.

Thanks for any help.