I am not sure if you are just looking for information relative to an Investment Advisor or relative to all the 401(k) plans services. Some of the suggestions here go beyond just the Investment Advisor, so please disregard if they are not applicable.
Mr. DeNoyior has come up with a good list, but here are a few additional questions and items that we would suggest which you request responses in writing. Since you are preparing an RFP, it sounds like you have that covered. Over the years we have found that front line sales people would like to be very accommodating, but the legal department and compliance at the firm prohibit certain clauses in a contract.
Ask if the investment person will be acting as a Broker or Registered Investment Advisor.
Who will we be working with, with their names and bios?
As part of your due diligence, one of the most important questions to ask is, "Will you accept fiduciary duty for your services in writing?" The answer to this question could tell you a lot about the provider. If the provider is willing to accept fiduciary duty, then hose fiduciary duties should be spelled out in detail. (note: There may be ways of minimizing your fiduciary exposure if you follow certain rules relative to delegation of your fiduciary authority).
Ask for a copy of Part I and Part II of the firms ADV. You may also look the firm up on the SEC website, http://www.sec.gov/investor.shtml , on the left hand is a link to check out brokers and advisors . Look through this form and you should find the ADV Parts 1 and 2. Look through that document especially ownership information and disclosures.
You can also go to FINRA.org, and look up the individuals who will be working with you, and print a detailed history which would include any disciplinary information.
Are the services bundled or unbundled, with other plan services (custody, record keeping, computer interface).
Are all of the investment in the portfolio actual mutual funds, which can be tracked on the exchange or are they Insurance Fund Accounts that are difficult to track on a daily basis.
Does the firm have an Fiduciary Bond and E&O insurance.
Ask for a sample plan portfolio with detailed information about the holding including TICKERS.