Do I need to replace both RAM sticks to upgrade to 32GB?

Yes, you’ll need to swap out both 8GB sticks for two 16GB sticks. With only two memory slots, you can’t just add more RAM—you must remove the existing 2x8GB kit and install a 2x16GB kit. Mixing a 16GB stick with an 8GB stick would run in single-channel or flex mode, losing performance, so get a matched pair of 2x16GB for full dual-channel bandwidth.