I'm planning to validate my visa in the last week of April. I'm planning for a two week vacation.
1. should I take any Medical inssurance? How is the medical benifits for new immigrants
2. I've a valid US driving licence, can I drive in Ausis with this?
how can I get an ausis licence.
3. what are the other necessary things can be done in 2 weeks

1 If you are a PR you will be entitled to medicare but that does not include ambulance cover. If you are doing dangerous activities holiday insurance should be considered.\

2 Yes. You only have to get an Aussie license before 3 months residence is up (as a PR). Check out the local roads Authority website for details. UK license holders have to take a written/computer based test to conver ones license.
For NSW check out www.rta.nsw.gov.au

3 have a good time and your passport with visa label might help.