How do I know my I-140 is approved?

My company document sponsor me I-140(EB2).The attorney submitted premium processing I-140 documents to USCIS on March 15,2011. Till now, I did not get any information.HR said USCIS can not find my Original PERM document.So USCIS changeg my premium processing to Regular processing.My questions are

(1)How do I know whether or not my I-140 is approved from USCIS web site?

(2)If my  I-140 premium processing was changed to regular processing,how long do I need to wait to know my I-140 apprval status?

Thanks in advance