How can I tell how big an SD card I can use in my device.

Thanks for the clarity on cards, JK98. If the 32GB came out of another device, I’d format it first anyway to FAT32. 

By the way, it won’t matter regarding the microSD card, but in general it wouldn’t hurt to update to the final firmware.

http://forums.sandisk.com/t5/Sansa-Clip-Sansa-Clip/Sansa-Clip-Firmware-Update-01-02-18/td-p/280756

Use the manual method, not the updater. If the updater is installed on your computer, might as well uninstall it.