autovacuum benchmarking ...

Hi Team

1. Can we know the how much time will take ongoing vacuum process  in DB?
2. Any benchmarking tool for vacuum process.
3. Can we know what exact operations has been done by Vacuum process.
4. I studied that only VACUUM process doesnot lock the table but due to
it insertion in table gets very slow. when i killed vacuum daemon
insertion get faster is it bug in 8.3.3


I know I should not ask all these questions in one go but i need
urgently its answer as vacuum process is just screwing my production
database. I would thankful for any suggestion on above  question...

Thanks in advance.
Regards
Amit