The stock basis will take a little bit of leg work but it is computed as follows:
Cost of the stock, plus all the dividend re-invested while owned.
So if you paid $500 for the stock, and had $223 in dividends over the time you owned it, then the cost basis is $723 in my example.
Another little tricky part is the last dividends received my be Short Term gain or loss as those would be held less than a year, while all the rest would be long term.
You can use "various" as purchase date, however make sure it is long term for the majority of what is sold, as this is better tax treatment.
Hope this helps.
