As my question states half my yard is taken over by crab grass, how do I kill it off, and rejuvenate my yard while preventing more take overs?
I come at things form an organic landscaping background, so we don't go for pre-emergents, which would prevent it from germinating next year. With that in mind, your goal is to grow the the turf grass thick enough to keep crabgrass from germinating and growing next year.
If your soil is bad, you'll want to address that. Have it tested by a reputable lab and they'll give you recommendations for amendments to grow grass.
In lawns that we maintain, we dedicate a couple of hours per week hand removing weeds - especially crabgrsss (clover isn't a weed, btw :-) ) Doing this you risk exposing the soil in those spots to sunlight, which could let new weed seeds germinate. That's why we always follow up with a handful of grass seed mixed in compost. The compost improves the soil and helps limit how much sun the weed seeds get, while the grass seed will germinate and fill the patches in.
Another important factor will be to mow your grass very tall - 3"+. This has all kinds of benefits for the health of your grass and it's ability to maintain deep, strong root systems. It also has the benefit of blocking more light from hitting the soil surface - again limiting the ability of weed seeds to germinate.
This fall after the crabgrass has died back, you would ideally do a lawn renovation. You'd rake out all the crabgrass, aerate if needed, then add a compost topdressing and overseed. Keep it well watered and it should be well established before winter. Every millimeter on which you can get turf grass to thrive is a millimeter where crabgrass cannot get a foothold.