Acct, or get Turbo Tax. Basically, if you owned it individually, you would 're-capture' all the depreciation that you should have been reporting over a 15 year life, then pay capital gains rates on the amount that is above the purchase price. Recapture is about 25% Federal, Long Term Capital Gains for Federal is about 15%, short term (2 yrs or less) is higher. So basically an accountant or Turbo Tax can figure this for you, or you can try to do it yourself.
After this, you gotta figure the NYS tax bite, which is different depending if you held it individually or through a corportation. Again, Turbo Tax and/or an accountant is your best bet.
As to lowering the tax bite- ah, now isn't that everyone's favorite goal?