请教小白兔，皮匠等大侠: H1 Transfer

I would like to transfer H1b to a new company. The company only provides the support documents, doesn't make full sponsorship. Please advise if I could do by myself. Which kind of forms I need to fill in, and how long will it take? If I hire an attorney, how much I should pay?

You help would be highly appreciated!

Thanks, and Enjoy the holiday!