You should not change the grade (by any more than 3 or 4 inches) around trees that you consider valuable. Root systems and root/soil relationships can be very easily damaged.

I also suggest that you don't use a rototiller anywhere near trees, even it would sure make for easier planting! That leaves you with hole-by-hole planting.

I don't have a recommendation for how closely you can plant your azaleas to the pines. Do you know what kind they are? I do know that azaleas do very well under the light shade of some pines and have seem them grow very well together.

You might want to consider asking this same question on the Tree Forum. It will be helpful to mention the species of pine as well as how many of them and their approximate size.

One thing to consider is the needle drop. The needles hang up in the Azaleas and it becomes a maintenance issue removing them for a tidy garden look. The longer the needles, the more of a problem it becomes. A groundcover that is vigorous enough to 'swallow' the needles is an ideal solution. So is just leaving the needles on the ground as a mulch. I have even added needles under Pine trees to make the mulch thicker to suppress weeds more effectively.

I'm a little late getting in on your discussion, but I think you are smart to plant the azaleas among pines, as long as they are Virginia, shortleaf, or loblolly pines (or other yellow pines). I'm not sure about white pines. Dogwoods and other shallow rooted trees like maples are not good companions for azaleas. My parents have 6 azaleas planted under 6 dogwoods and they bloom unevenly and have lots of dead spots. I'm attempting to attach a photo of the 45 year old formosa azaleas I inherited with my house planted as close as 4 feet from loblolly pine trees. {{gwi:398068}}