Timeline for USC sponsoring parents

[anonjain]

I would like to get a green card for my parents (living in Delhi). They already have a tourist visa valid till 2008. I live in New Jersey. What is the quickest risk-free way to get them a green card?
1. If I apply when they are in India, how long does it take for the I-130 to get approved, and how long does it take for them to get the green card (or something equivalent) after the I-130 is approved?
2. If I apply when they are in the US on tourist visa, how long does it take for I-130 approval and adjustment of status?
3. Any other risks with either approach?

Thanks

[immihelp]

It is better to do consular processing for them. Everything will be done between 6 months and 1 year.

AOS takes years.