Rear suspension work

I have a 99 4wd Astro that we use for camping and hauling the jetski to the lakes. The rear suspension has always ridden a bit low compared to our previous Astro, but the Chevy service folks have insisted that it is within new specs.

I would like to raise the rear a couple of inches, increase it's load carrying ability so it doesn't sag so far with 3 kids, 2 dogs, and all the cargo loaded up. It would be nice to improve the ride and handling under heavy loads as well.

So, I am wanting to add a helper leaf spring, add an anti-sway bar, and install premium shocks.

Is this something I can do in my garage? I am mechanically inclined but I've never taken on a heavy project like this. Can one person with reasonable tools do this kind of work? I don't mind buying a few reasonably priced tools like large wrenches, etc, but I don't want to have to invest lots of dollars in specialty tools.

Do you have any particular brands to recommend, or to avoid? Any advice or other suggestions on doing this job?

Back in the '70s, a friend got some helper springs (an extra leaf) done at a spring/ suspension shop. I was surprised how cheap it was back then.It might pay to phone a shop first.