ref Ngorogoro, I might suggest it is better to see if you can get a seat in one of the safari tours and go into the crater as taking your own car is in as said, hellishly expensive, and not really worth the money.
Also don't do as i did, and pay $140 dollars to drive into the reserve and just view the crater from the top - biggest rip off of my life. You can only stick to the main road, which is so badly corrugated it caused serious damage to my Landy rover, there is very little wildlife to see (saw an elephants arse and a zebra), nowhere to stop, and there are only a couple of small car parking points where you are able to see a hazy view of the crater. Most expensive photograph of my life.
Also the road on through to the serengeti is in extremely bad condition (so bad, my shock absorber punched a neat hole through the axle mounting within two hours on it) and we had to turn back as it was getting too damaging and highly uncomfortable (and we have driven her from the UK on some of the worst roads in Africa!)
In terms of value for money, I've found that the parks in Tanzania are way overpriced and can be pretty poor - compared to the $120 we paid to spend an absolutley action packed day in Masai Mara in Kenya (who don't insist you take a guide and give you much more freedom to roam around the park)

Rant over have a great time there! Tanz is a great country and there is lots to see and do, we are particularly enjoying the coast at the moment : )

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