Is this miata a good deal?

The price is about right. I would suggest a trip to http://forum.miata.net/ and doing some reading on what to look for. The primary one is does the crank wobble. Take a magnet along to check the areas behind the doors down low (dog leg area of wheel arch) for body filler. Also the lower portion of the body paint should have some texture to it. If not then it is not original paint.

I would suggest finding a engine to rebuild. I know that Mia ta engines can last 300000 miles, but if you want to autocross a fresh engine is a must.

You need to find out when the water pump, seals, and clutch was done last.

If it has the factory header still on it, there is a good chance that is where most of the lifter noise is coming from. I have had to replace all of my factory headers on my Mata's and replacements can be as expensive as you what to pay. 4-2-1 headers are a nice up-grade any way.

$3000 is a lot of it to me. The first year model has a problem with a 'short nose crank'(search). If the crank pulley wobbles then it has a major problem.

Check for rust.