We need to know more about where you live. For now I'm going to assume you are somewhere between Bakersfield and Modesto in the Central Valley. If you have fescue there, you really should get rid of that and replace it with a warm season grass like bermuda, hybrid bermuda, St Augustine, or UC Verde buffalo grass. These grasses are much better adapted to the heat of the Central Valley than any of the northern grasses (fescue, rye, and Kentucky bluegrass). When you try to grow cool season grasses in the heat, you end up using more and more water to keep it alive as the summer progresses. When the summer heat thins it out, then weeds come in and you end up spraying out the weeds. But if you grow a turf that is adapted to heat, it will become more and more dense in the heat and help to keep weeds out. So one of the first rules to success in gardening is to grow plants well adapted to your location.

If you want to test your soil, I suggest not going to the county agent but go to Logan Labs instead. Their $25 test will tell you much more than a county agent, or UC Davis test will. Post the results of the LL test on this forum and you'll get about $200 worth of free advice.

Assuming you are going to go with one of the warm season grasses, you can start now. If you decide to put down sod, that can be done any time in your area. All the grasses I mentioned are available as sod. Common bermuda is also available as seed. If you want to seed common bermuda, that has to be done ASAP or you will miss the heat window of summer. Bermuda seed germinates best when the soil is the hottest. If you put it down and do not have 80% germination in 5 days, then you missed the window. You'll still get coverage, but it might take a few weeks longer. If you decide to seed common bermuda, you will need a certain amount of seed to cover the area. I would suggest using a mix of three bermuda seeds which total the pounds of seed needed for your area. I would suggest Princess 77, Yukon, and Riviera.

These warm season grasses need full sun with the exception of St Augustine. It can grow well in the shade of a building, fence, trees, and shrubs. The others will all thin out in those conditions.

As for the reno itself, do NOT rototill the area first. Start by spraying out the existing plants with RoundUp. Spray it one week and start to water daily for 5 to 10 minutes. The idea is to sprout all the weed seeds that might be there. A week after the first app of RU, spray again to get the new weed sprouts. That should get almost all the weeds and give you a good start. Once everything is dead, rake it up or scrape it off. The best thing you can do to prep the soil is to run a tractor and box blade over it. That would take less than a morning and it would be done. If that is not in the budget, then look for the high spots and scrape those down with a hoe. Move that loose soil into the low spots. If the low spots still need more lift, you can do that with topsoil or sand. You probably do not need to bring in more topsoil. That is almost always a mistake for a yard that is already graded. After you fill the low spots with soil, water it down and check again for low spots. Fill, water, and check until you think it's perfect. At most 3 times should be all you need.

If you're going with sod, you're ready. Once the sod is down, roll it with a water fillable roller to ensure the bottom of the sod is in contact with the top of the soil. Then water 3x per day for 5 to 10 minutes to keep the surface of the soil moist, not mushy. Do that for 2 weeks until the roots knit into the soil. Then start to back off on watering frequency until you are applying about 1 inch in two applications. At that time you can mow. If you have St Augustine or UC Verde, those can be mowed at the mower's highest setting. Hybrid bermuda can be mowed at the mower's lowest setting. I believe the UC Verde can be mowed very low, too, but I have not seen it.

If you are seeding, then scatter the seed. You'll get more even coverage with a drop spreader, but if you going with bermuda, it doesn't really matter. It's going to all be covered in 2-3 weeks anyway. With the seed down, roll it with the roller to ensure good seed to soil contact. Water the same as for sod. You'll have a lawn in 1 week and be able to mow it in 3 weeks. Mow to the middle setting on the mower.

At the same time you apply the sod or seed, you can fertilize with an organic fertilizer. Organic fertilizers are "slow release" which means the nutrients begin to get to the plant in 3 weeks. Both seed and sod can easily go 3 weeks without any fertilizer, so the timing works out well. I would recommend soybean meal, alfalfa pellets or meal, corn gluten meal, or corn meal at a rate of 15 pounds per 1,000 square feet. You can get those in 50-pound bags at your local feed store for about $15 or less. Call ahead to get price and availability. Plan to use it all by the end of the growing season. It can be applied any day or every day, any time, rain or shine, without fear of hurting anything. These organics work through the soil biology, so they don't need special instructions like chemical fertilizers do.

I probably have not covered everything. What questions do you have about what I've said and what I missed?