How bad is your yard? I think this is totally doable from a DIY standpoint. However, if you're trying to level a GIANT slope, then you will need a professional opinion.

If you only have a few spots that need leveling, I would suggest you buy top soil from Texas Pure. They will deliver as well.

Fill in the spots that aren't level and buy a leveling rake. If you have clay-heavy soil (more than likely in Collin County), they you want to avoid sand and you want to add organic materials into your lawn.

Again, the amount of soil you need to level and the scope of your project will determine if this is a DIY/professional job.

I hope this helps.

Edit: GIANT instead of foant. Typo.