Yes, it's pretty easy. Are the existing boards nailed or screwed down? If nails, pry the boards up; if screws, get a power drill and back them all out. Lay the new boards down, screw them in, maintaining a 1/8" gap, and you're good to go. There are some tips and tricks, but that's the gist of it.

Composite boards often need closer joist spacing than wood (i.e., 12" on center instead of 16"). How far apart are your joists?

If you post some photos, that might bring up other recommendations to share that apply to your specific deck.

Thanks Weedyacres. The existing boards are nailed down.
I think the joists are 16" so if I went with composite, I'd have to have some added. That's something to consider.

I'm playing around with ideas right now so I would probably put the job off until next spring when I had time to do it (and it's not sweltering hot out).

Appreciate the info!

From experience, if the nails will not come out on the first try, pound them in to loosen before trying to pry them up. If you just try to pry without loosening them you might just pull the heads off?

My contractor just pried up the nailed boards; much faster than addressing individual nails. Ugly, dirty work but nothing a DIYer couldn't do well.

If you aren't worrying about the damage, just prying up the deck boards with the biggest bar you can find it the quickest way.