If you're a first-year staff, I, as a senior, wouldn't expect much from you except the basic knowledge of defined benefit and defined contribution plans. It's ridiculous to expect you to read the guide. When I started on Bps as a staff, the big thing for me was to be able to read and quickly find info in Plan Documents (clients give you a copy so it should be somewhere in the prior year work papers). Not something you can do over the weekend but being able to find info is VERY helpful. It's legal language.
You will be helping with rolling forward prior year work papers, doing the testing, and following up on any discrepancies. So read online about DB and DC plans. Depending on the materiality and the client, you will most likely be testing benefit payments, employer and employee contributions, loans to participants, participant account information, transfers of participants' account balances for DC plans and benefit payments, participant account information, benefit obligation, employer contributions, investments valuation, administrative expenses for DB plans.
A few things. Remember that IRS sets the limits every year for various things, for example, maximum amount employees can contribute during the year, etc. It would be nice for you to show that you are aware of that and look it up. You'll need that info for testing.
https://www.irs.gov/Retirement-Plans/Plan-Participant,-Employee/Retirement-Topics–401k-and-Profit-Sharing-Plan-Contribution-Limits
https://www.irs.gov/Retirement-Plans/Plan-Sponsor/401k-Resource-Guide-Plan-Sponsors-401k-Plan-Overview
Also be aware of DOL guidelines. It may or may not come up. For example, there are certain exceptions of how military personnel is treated if they are called for an active duty.
https://www.dol.gov/ebsa/newsroom/fsreservists.html
I honestly can't think of anything else. It's a lot and you learn it as you go. Your seniors should train you. It's a part of their job after all.
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