One possible version 

Dear Tim,

     I've received your email, asking me about my plan for the summer vacation. Now let me tell you

something exciting. 

     I've applied to be a volunteer for the World Expo 2010 Shanghai and I'll start working as soon as

I have finished the entrance examination.

     The exposition is a grand international gathering, which is expected to attract 70 million visitors

from both home and abroad. And what makes it unique is that it is being held in a deVeloping country

for the first time. Can you imagine how proud I feel to be able to do my bit for this special occasion?

     Speaking of the volunteer work, I'll mainly help out in Beijing Pavilion, where I will show the visitors

around and introduce the magnificent buildings to them, such as the Forbidden City, the Bird's Nest

and so on. It'll be a good chance to help the visitors to get to know about the culture of Beijing. Apart

from my work as a volunteer, I will certainly pay a visit to different pavilions. I won't miss seeing the

great inventions and achievements on display and I can experience different cultures as well as exchange

ideas with people around the world. Sounds fantastic, doesn't it?

     I hope you can come and see it for yourself. 

                                                                                                                                Fondly Yours, 

                                                                                                                                Li Hua