Now for your real question...I'll get to the "what will we do in heaven" issue a piece at a time. First, remember that even though we may serve differently and longer in the life to come, serving the Lord here is important. Jesus didn't say to the sick, "Get over it. You'll be dead and in heaven soon, so your illness doesn't matter." Rather, He healed them and comforted them in the "nasty now and now." This life is not the ultimate life, but it is life, and your chosen profession can be used to serve, minister, and lead many to Christ, as well as comfort the sick. "Voice boy" can also have a ministry in this life if he decides to use his talents for God.

Second, remember that there's another step before heaven. When Jesus returns after the tribulation, He will establish His kingdom upon the earth for 1000 years. That will be a literal, physical kingdom with real people and real needs. Although all of us that were saved prior to the rapture will have glorified, perfect bodies, and those believers who died during the tribulation will also be resurrected, there will be multitudes who were saved during the trib who go survive until Christ comes and go into the kingdom in normal bodies. These folks will be normal, so they can get sick, feel pain, need health care just like people today. They will also marry, have children, and eventually fill the earth with non-glorified folk. We also know from Scripture that Christ promises to use us who are saved now to serve and administrate in that kingdom. Therefore, the scenario of God using your calling and skills as a nurse in the kingdom is quite feasible. That's a millennium of service before we even get to heaven.

Now then, after the millennium, every saved person is glorified, and every unsaved person is cast into the lake of fire. All living people then are perfected and no longer susceptible to illnesses or death. What becomes of your calling/gifts then? I'll be honest, the Bible doesn't say a whole lot. The Bible is clear that we will worship (Rev. 4-5), that God will teach us of His grace (Eph. 2:6-7), and that we will enjoy His presence forever, but as to exactly what activities will be performed, I'm not sure. I will say, that since, as you pointed out, there will be no sorrow or sadness, you will not feel like you wasted your time studying nursing, nor will you be jealous of those who took voice lessons. My guess is that our lives will be so wrapped up in God that our previous lives here will seem like distant memories. We will wonder how we ever got along in an existence without the physical presence of the one who saved us. Old things will, quite literally be "passed away, ... all things are become new." (2 Cor. 5:17)

Here's an illustration I've been thinking about lately. When a baby is conceived, and begins to grow, his whole world is the womb. He knows of nothing outside of the walls which encase him, though he hears the occasional voices of another world outside his own. One day, he experiences the pain, discomfort, and terrors of birth, and a part of him probably is very fearful of the changes, and wonders why he can't stay where he was. Once born, however, his previous life inside the womb is so paled by comparison to the light, love and joy that he is now capable of experiencing, he quickly loses all desire for that previous life, and is consumed with the joys and expanses of his new world with his parents. In the same way, we live here in this world, and work, play, experience, etc., and do what we can for the Lord. But one day, we will be "born" into a new world, where the glories of being with our Heavenly Father are so dramatically better than the "sounds" we hear of Him now, that we can't imagine ever regretting our previous life, or desiring it. That doesn't tell you how or if you will use nursing skills in heaven, but hopefully it does tell you that no matter what heaven is, the best part is being with God. Live your life here with that world in view.