Can excise be claimed against service tax

Hi

     I am  an accountant for automobile dealer( our company sell  two wheeler vehicles to an end consumer). I have a doubts  regarding CENVAT Credit rules. Please Clarifiy  my doubts.

We pay the  excise duty to our supplier  when we purchase the vehicles as well as  we are attracted service tax  because of we provide the serivce of motor vehicles under brand name. My quesiton are

1)can i utilise  the input of  excise duty  against the service tax liabilty ?

2) if so, shall i go for  registraion of  frist stage or Second stage dealer ?

Thanking you

P.Venkateswara Rao

(Accountant)