The question is - when you became owners of the property?
If the property was inherited upon your mother's death in Sep 2007 and you became the owner at that time - inherited property would have stepped-up basis that is a fair market value of the property at the time the decedent died.
If you receive the property as a gift from your mother (while she was alive) eight years ago - the basis would be the same as your mother had at the time of gifting - thus if your mother purchased the property - the purchase price generally constitutes the basis.
As you sell the property - the selling price will be reported on the form 1099-S - http://www.irs.gov/pub/irs-pdf/f1099s.pdf - so the IRS expects you to report the sale transaction even if you do not have any taxable gain.
You will report it on the schedule D - http://www.irs.gov/pub/irs-pdf/f1040sd.pdf - part II
The taxable gain is calculated as (selling price) - (basis)
The basis should be adjusted by any improvement, selling, and some other expenses.
Please let me know if you need any clarification.
The capital gain is calculated the same way in any situation - as (selling price) - (basis)
The only difference is - how the basis should be determined.
If your mother set revocable trust - she still considered an owner of the property (the title was not changed - correct?). But upon her death the trust became irrevocable .
Putting the property into the trust in such situation is not a gift - as you did not became an owner - correct? - and your mother still had an option to dissolve the trust and take the property back.
If all above are correct - and you became the owner only after your mother died - the property is considered as inherited and the basis is a fair market value on the day she died.