I don't have any good news for you. Starting with what you've already done, yes, everything is incorrect or out of order.

First off you rototilled. That will ruin everything you plan to do for the next 3 years as that fluffy soil that looks so nice settles again and forms a new structure. If you put the sprinklers in now, in 3 years they will be standing up higher than the soil by as much as an inch. It will settle, unevenly, beginning now as it gets watered and the microbes in the soil regain their numbers. Grass roots will help form the new structure, so don't wait on getting grass in. 2,800 square feet is not that much. You can cover that easily with one oscillating sprinkler, so sprinklers can wait (IMHO). So with that in mind here's what I would do...

1. Level with a drag. Wet down to see where the low spots form and drag again to fill the low spots with the high spots. Wet it down again to find the remaining low spots. Rinse and repeat until you get it pretty good. You may as well start out with a flat surface even though it's going to change. Take pictures and notes, because this is how you will be releveling again in 3 years. Seriously, rototilling will haunt you as your lawnmower bumps along getting worse and worse as time goes on.

2. Water it 3x per day, every day for a full week to sprout any new weed seeds that have not yet sprouted.

3. After a week spot spray any new growth with RU. Skip this step and all the new weeds will sprout into your new grass seed.

4. Sow seed and roll it down to be sure the seed makes good contact with the soil.

5. Start watering 3x per day, every day. This watering only needs to moisten the surface. Do not let it run and make the ground soggy. If you're using an oscillator sprinkler this can take some time, but other sprinklers apply water faster.

Notice there's no scratching the surface or any of that. Rolling the seed down takes care of seed-to-soil contact.

Hydroseeding is a gimmick for homeowners. If you had a steep embankment to seed, then sure, hydroseed it. But if you have relatively flat ground the hydroseeding is overkill. Scatter the seed with a broadcast spreader.

Three years from now you can reconsider the sprinkler system. When you dig the sprinkler trenches that's the same as rototilling. All the dirt that comes out of the trenches must go back into or on top of the trenches. If you scatter it around then in 3 years you'll have low spots that run along the trenches. So mound it up on top to get all that soil to settle properly.

Now that I've said all that, it could be only some of this applies. Where do you live? and please tell me it's in the north or north of Tennessee.

Thanks for the info. I'm located just north of Montana, in Canada. No doubt, tilling may have not been a good thing, the ground had been tilled prior and was excessively weedy so I figured it was the best of a bad situation. (house is 5 yrs old, we bought late last fall). I think I'll still do the sprinklers as I can place them at a lower depth than recommended to allow for compaction of the soil. That combined w/ top dressing if needed to change the elevation or digging them in deeper (later), should it be needed. Re-digging and adjusting elevation of the sprinklers won't cause any more damage to the entire lawn vs digging the entire system in later?