Question
We are having a 2800 sq ft section of our front lawn in Winter Garden, FL replaced with St. Augustine and the companies that have given us estimates differ on how they will go about doing this.  A couple of them will use a sod cutter to cut out the sections; others say they will kill off the grass first, wait a week and then come out to cut the sod out and replace it.  What is the best way to do this?  Also, we have a combination of crab grass, bermuda and st. augustine in our back yard (which is the same issue with the the front yard section). Should we have the entire back yard ripped out so we can put st. augustine seed down (since we cannot afford to put sod down there, since it's around 5000 sq ft)?  We're afraid when we mow the lawn we'll "contaminate" the good front lawn with the inferior back yard grass.  Thank you so much for your input!!  Incidentally, we didn't create this disaster lawn...the previous owners could take credit for that.  

Answer
Ms. Mais:

The main issue for laying sod is having a clean, level surface on which to place it.  If you have a lot of weeds, it may be worth the step to spray them to get rid of them for a season or so.  Your choice.  I would make sure that no Bermuda or other summer grass survives in the front yard to compete with the St. Augustine.

In the back, I would replace the old one with St. Augs, as you suggested.  You are right about contamination.  The lawn mower deck holds a lot of seed and sprigs to spread around when the cake on the underside dries and the mower is run again.

Use a good herbicide on it before preparing it for seed. You can also find excellent varieties of St. Augs seed.

Best wishes.