SF 3107 (or the 3102) is an application for immediate retirement (nondisability). Do you qualify for an immediate annuity under FERS either as an MRA plus 10 or MRA plus 20? If you do, you might want to file this form as a back up to your disability retirement on the basis that getting some money while the disability application is being reviewed is better than getting none at all.
SF 1152 is a designation of beneficiary form for unpaid compensation. If you keel over before this is all settled and your agency owes you any money, they will pay the person that you listed on this form. Not critical for your retirement, but there is no harm in completing it and it could expedite the separation process, if you disability retirement application is approved. Your agency probably has a checklist of the forms that separating employees need to complete and if this form is missing, it could hold up your separation. OPM won't pay you until your agency notifies OPM that you have been separated.
SF 3102 (or 3107) is a designation of beneficiary/survivor election form for FERS. If you are married, you definitely need to complete this form. If you are not, then it is less critical. If you are married and elect less than a full survivor annuity for your spouse, you likely will need to have your spouse's notarized signature on it.
SF 2817 relates to your FEGLI and what life insurance, if any, you wish to carry into retirement. Completing this form will expedite the determination of your net annuity. There is also a designation of beneficiary aspect that you should review as well.
FedMAR allows OPM to quickly obtain info about the status of your claim for SSA disability benefits. Definitely complete this form ASAP. This one can be a read deal breaker with OPM.
The WP-4 is a tax form similiar to the W-4 form that you complete to determine how many exemptions to claim for tax withholding purposes. If you don't do this one, OPM will initially deduct income taxes as if you are married with three exemptions. That may of may not reflect your actual tax liability. If it does not, you probably want to complete this form and get your tax deductions correct from the beginning.
Most of these forms are one or two pages at best, plus instructions. They are not difficult forms to complete, but there can be some requirements, such as the notarization one or some calculations that you need to make, such as with the WP-4, that could take a little time. I also would go over with your HR person, the various costs associated with any FEGLI elections that you might make. Many new retirees are unpleasantly surprised at how expensive FEGLI can be. Often, it is because they did not take the time to understand the costs associated with the FEGLI decisions that they made on this particular form.
Most of these forms, except FedMAR, can be download from OPM. Go to
www.opm.gov/forms and click on the forms in question to get an idea of what actually involved with each form.