My brother was named executor of my mother's estate. She died suddenly in April '08. Her trailer was just sold and I received a check through the estate account for $5.000. I know in PA there's a 4.5% inheritance tax. Where do I get the proper forms to file claiming this inheritance so I don't get in trouble? Also, does this money also have to be claimed on the regular income tax forms we fill out each year? Thank you.

You do not need to include anything having to do with inheritances on your income tax, so no worries there.

As for PA inheritance tax - the tax is 4.5% on the value received by direct descendants. It is the executor's responsibility to pay this out of the value of the estate, before he makes distributions to the heirs, so presumably your brother should have withheld the appropriate amount before he sent you the $5K check. You may want to verify with him that he did this properly - if he neglected to do this, he may now need you to return some of this money to the estate so that he can pay the tax. The form must be filed within 9 months of death. There is also a $3500 family exemption available. For further info, forms, etc see:
Pennsylvania Department of Revenue