Bad idea to work on equipment when it is powered on. It is best to turn off power to the receiver/amplifier before messing with any wiring and/or components, including your speakers. It is easy to blow your equipment if the wiring were to get shorted or crossed.

If you need to replace the tweeter, turn off power to your equipment, unplug the speaker, and replace the tweeter. Before disconnecting anything, take pictures of the wiring and the back of the driver to ensure correct polarity when reconnecting. Inspect the crossover to ensure there is no visible damage. Reassemble the speaker, connect everything, and turn on power.

If you need to work on the woofer, the same procedure as above should be followed. It may be that the surround is split or degraded. A visual inspection should indicate if the woofer needs to be refoamed. If you need to refoam one, do both. A visual inspection of the spider after removing the woofer will indicate if that needs to be repaired. If the problem is a rattling sound, a visual inspection should identify if anything is touching the back side of the cone.