depending on the motherboard manufacturer, all you may actually need is a USB thumb drive formatted to FAT32 to save the ROM update to and be read from as some implement a method of flashing updates directly from USB thumb drives from the motherboard’s ROM. Both ASUS and MSI do this and my old ASUS P8-H61M LE/USB3 board from back around then certainly had the feature.
the CR2032 type CMOS battery would certainly be worth changing now regardless, if you can acces it as they don’t last forever. just be careful when doing so not to damage the contacts. also make a note of all firmware settings not set to auto beforehand and have a clock handy to reset the correct time afterwards as you need to swap batteries with mains power off and any removable external battery disconnected as well to avoid shorting the laptop’s motherboard.