If your trim fluid is low, certainly you need to add fluid to the proper level.
If your trim fluid is milky (water intrusion), then certainly you need to replace the fluid AFTER you find and repair the leak.
Under normal circumstances, the trim fluid should last the life of the motor and never need changing.
Regardless, the tilt support is a dumb part. If you want to do right without harming the equipment, buy a "m-y wedge" or a "transom saver".