I'm about to replace a my girlfriend's lawn that's heavily infested
with crabgrass.

What's the best approach to doing this? Some of the different
suggestions I've received are as follows:

- Spray the lawn as it is (without digging it up first) with
preemergent and then cover it with a tarp for several weeks before
digging it up
- Remove the top layer of grass before spraying it
- Not spraying it at all

I guess I have two basic questions - do I really need to take off the
top layer of dead grass before spraying it and do I really need to tarp
it after spraying it? Any and all suggestions will be helpful.

Christopher

P.S. I live in Northern California if that makes a difference.