1. Good call! Make sure you have lots of bunches of stem plants, enough to plant 60-70% of the tank floor. It's going to look very crowded, but you can actually replace a few of those plants once the soil matures in a few weeks.. for now, these are very necessary to keeping the water parameters good, absorbing nutrients from the soil, etc.
You will probably need to sift the Miracle Gro (make sure it's the organic one without water retention stuff in it..), as it has a LOT of chunky wood bits that aren't ideal, the soil is pretty great though, I've heard a lot of good stuff about it.
2. You don't need much sand on the sides, if you're concerned with how it looks (which is the only function of doing this) - just enough to hide the dirt. Try to pile more up the back than the front, for perspective. Whatever depth of soil you have, halve that in sand - don't go over two inches for soil, though..
3. It's better to keep the sand intact as a cap. I put a small plate in for these initial fillings, and dump the water on that so it doesn't mess up the sand too much. Don't panic if it mixes a little bit.
4. When I said 'a few inches of water' I meant fill it to this level for planting. Trying to plant stuff in a full tank is a giant PITA, as some plants are very buoyant. You might find some tweezers handy for planting smaller plants, just poke 'em in - much easier than fingers!
Oh yeah, and don't turn the heater on yet. ;)
5. Nope. Plants will hate it. Use dechlorinated.
6. I wait a couple days for everything to settle before including the fish. The tank will cylce on its own eventually, and the plants will start taking up ammonia once the soil is mature and they start the growth boom (you'll see what I mean in a few weeks..) -- prior to the soil adapting to aquatic conditions, you'll need to test the water regularly and make a couple of large water changes per week to deal with the ammonia and other stuff coming off the fish/soil.
Do NOT stock heavily at this point. Maybe six fish, max? I only have one fish and a few snails in my 10g and I still worried about excess nurtrients for a while..
So basically, treat it as an uncycled tank for a few weeks, test and test again, make lots of water changes. Once you see the ammonia/nitrites at 0 and the plants are growing like jiminy, you can be pretty sure it's safe to add the rest of the fish and start cutting back water changes to maybe one a week for a couple more weeks.
7. I think it really depends on how much stock/what kind of plants/how many plants/adequate lighting for the plants --- you will need a test kit and monitor the tank yourself for ammonia/nitrates and so on, and make changes accordingly.
I still filter (sponge filter, for a little water motion and extra beneficial bacteria) and do 25% water change weekly, though my soil is mature. That's my preference, probably not necessary but I feel better about doing it that way and it's no real effort.