I changed company in 2008 will I need to take W2 from old employer also to file the tax returns as the new employer W2 form has the details of wages and taxes of the new company.

You must report all your income for 2008. Yes, you need W2 from old employer. They will mail it at the address in their records.

Note that mailed W-2s are NOT normally forwarded to new addresses, so you may need to contact your old employer to give them your new address.