Cost basis for employer-matched stock contributions, dividends

[San Pedro]

I'm trying to find out how certain distributions from my
401(k) company stock will be taxed. Using net unrealized
appreciation rules, I understand that I will be taxed at the
normal rate for the cost basis of the stock in my 401(k) if
I withdraw that stock, but what counts toward that cost
basis:
1) only my pre-tax contributions?
2) also the employer-matched contributions?
3) how about reinvested dividends? (and what if I cannot
find the records for all of the reinvested dividends?)

And does anyone know whether New York and California tax
laws treat this differently than federal tax laws?

Thanks for your help!
--Padraic