Switching from Post study work PSW to Tier 2 Dependant

Hello Gurus,
Please I need urgent help on the following.
I have been on UK student visas for 9 years, My PSW visa expires soon.
My wife is on a 3 yrs Work Permit Tier 2 and I want to apply as her DEPENDANT (TIER 2 DEPENDANT)

1)Can I do so whilst in the UK? or do I travel abroad?
2) What form do I require?
3) any UKBA links you provide will help.
4) Any advice on 10 year long Residency?

Many Thanks in advance.