Bring Your Wallet
Procurement is, uh, big business. There are lots of details in procurement planning, the creation of procurement documents, bidder conferences, and in the contracting of the work. All organizations have their approach to procurement and contracting. You, the project manager, need to understand your organization's approach and then follow the rules to get the stuff you need.
Now, if you'll excuse me, my Spanish-speaking, CCIE-certified, COBOL programmer has spaghetti ready. And I need to pay his invoice.