planning a shopping for business trip

I think you can go to GZ and Shenzhen for finding the manufacturers.
For the exact district of these manufacturers in these two places, it depends on what kind of electronical items you want to purchase.
For the places to stay, you can stay in Home Inn and Hanting Hotels in either of the two cities. There are many branches for these two hotels in both of the two cities and you can find a nearest one to you.
It is hard to tell you the cost for your trip, which depends on what kind of activities do you do in the seven days. For the living expense, you may need to spend about 900 to 1000 RMB, if you live int he hotel I suggested. The food price is not very cheap in these two places.