Cable broken inside.

No you can not and you do not want to do that my friend. That the good thing about the iPhone 3gs compared to the original iPhone. Theses parts can simply be purchased online. Whether from ifixit or ebay. If you order it from eBay, you will pay about 2-5 USD for the home button cable and 10-20 USD for the speaker. Now for the speaker, there are three parts: the buzzer ringer, the antenna flex cable, and the dock connector port flew cable. You can buy all three done for you or you can buy them separately. I would buy them seperately because they come out cheaper if you buying foreign. but if the item you are purchasing is from America, buy it already done. I hope this has been of great help to you.