Punch out Catalog in MM (PR and PO)?

Hi, 

I have been asked to  give the feasiblity  of setting up the Punch Out catalog functionality    via MM  .

I.e.  in PR  or PO creation  the user should  click on the Catalog icon and  it should direct him to  a Vendors catalog , there once  User selects the Items    the details should be  transferred back to the PR ./PO document.

There is no SRM/MDM system involved,  we are not using PM/CS catalogs either.  Its purely  MM catalog  set up required.

I have gone through various Posts/ Sap notes  but  none  gave clear directions on what all is required to set up this functionality purely from MM side.

(The SAP note says that this is  a Consulting and chargable  service?)

All I know is that we have to Set up the OCI  details on the Vendor catalog  in this node.

More questions :

1- The information to be maintained in this node, needs to be provided by the External Catalog provider?

2- Does this  work  only for text based items  or  does it also works for Items with SAP Material codes?

3- If Yes for material codes,  do I need to maintain some mapping somewhere  between SAP material code  and item code passed by the catalog?

4-Can I use Multiple catalogs without any additional Code/BADI implementation?