If you are "Truly" Pre-Approved then you would these items:
1.) Copy of a Pre-Approval letter than spells out your loan type and term, maximum sales price qualified for, maximum interest rate qualified for, expiration date of the letter.
2.) Copy of you Itemized Fee Work Sheet that has all costs (including the lender's fees), estimated interest rate (based on that days pricing), and payment.
3.) Copy of your VA AUS (Automated Underwriting System) Findings. By having this document, you can see upfront what conditions you will be excepted to supply the lender and you WON'T be caught off guard in the 11th hour.
If you don't have the warm and fuzzies about your Loan Officer, I suggest you look around. Make darn sure you properly vet your LO, as your choice in who you work with will greatly affect the end game and specifically if you will get a set of keys.