How can I replace the internal speakers?

@atsi download the Hardware Maintenance Manual for your computer from here It'll help with working on your computer. Here is the Lenovo Video for the speaker removal. My concern is that this may not be a speaker issue. Always check your software settings. Make sure that your speakers show up in your devices. I would even suggest to update the drivers for those.

Try some external speakers and see if those function okay. Try a headphone and make sure that that is working. A stuck headphone jack can also be a cause since it will turn the speakers off whenever headphones are connected.