thinking about switching my 29g to planted

hi, since you don't want high maintenance plants (for which you'd need new lights and CO2), I'd say go with things like java fern, java moss, Anubias, anacharis, water sprite, wisteria (I've got all of those and then some ). Here's a great site that will let you search aquarium plants by difficulty and light requirement http://www.plantgeek.net/plantguide.php

As for vacuuming the gravel, just leave the substrate around the plants alone. I just swish the vac over the gravel there, but don't bury it into the substrate. You're right, you don't want to mess up their roots. It can take a long time for good root structure to grow, and the plants would not appreciate having them ripped up every week

The combination of plants is really up to you. As long as they will survive under your conditions, then it's all good.

what do you mean by "best way to install"?

you could always try it without special substrate first. I've got plain ol' river bed gravel in my tanks right now and most of my plants are doing just fine. The ones that aren't are the stem plants that I received as clippings. When I tried to plan the stems, they rotted under the gravel and took forever to finally grow roots. But plants that I got with adequate root growth on them are not having problems.

If you had to change your gravel (or at least remove it all so you can put a layer underneath), you might want to take out all your fish. Plant substrates are pretty dusty so might leave particles in your water, even after plenty of pre-rinsing. Hopefully someone else can give you a recommendation on that one.

I was thinking about adding some plain laterite to my existent gravel, rather than layering it underneath. That way I could leave my fish in and just mix it in during a water change. Someone can let me know if that sounds like a bad idea.

As for planting, just dig a little hole in the substrate. Plop the plant in there, and cover it back up. I try to leave a little bit of the roots exposed above the gravel, as opposed to piling gravel around the base of the plant. I think that helps because it allows the plant to get some nutrients from the water around the top of the roots (gravel does not hold onto nutrients), and prevents the heavy gravel from suffocating or crushing the roots.