First welcome to Dalian, and wish you will have good time. Well, as a local person, I would give you some introduction about living here in Dalian.
1. To compare with other cities in Liaoning Province, DL is kind of the best environment city. Buttt, if you compare with your hometown or Japan, you may disppoint. In the morning and evening, the air polution is kinda bad,so if you are planning jogging or riding bikes, ummm, not good.
2. Traffic jam. We have really bad traffic jam here. The rush hour is from 7:30am-9:00 am, and 5 pm to 7:30 pm. I guess you are not coming here for work, then you may not need to worry about this. Coz everday and night when I go to work or come back home. The traffic jam is really anoying.
3. Windy.... Quick weather change. Here because we are by the see side, especially the days when you are here, our city will be very very windy. And weather can change very fast. So you may need to prepare some thick and thin clothes together.
4. Prepare a lot of Chinese RMB, i mean cash. In China we dont use credit card a lot. If you go big shopping mall or supremarket then you can use credit card. But, normally if you just buy thing in small shop or eat food at small place, we only use cash.
5. If you wanna use facebook, youtube this kinda of stuff, you may need to install VPN first. This can help you connect with you foreign website. Actually except these kinda of app, we do have access to many many foreign websites.So no worries.
6. I guess you may need to buy a cheap mobile phone here during those few months. Ask your friend to take you to cheap store, and you can just buy a cheap one maybe around 2-3 hundred yuan. Then you can just throw it when you leave China.
7. BTW, I speak Japanese and I deal with Japanese customers before in my last company. Between Japanese and Chinese, we have huge differences, so your experience in Japan may not help you here in China. sorry.
8. Chinese do welcome and like foreigners. So if you try to talk to them and smile at them, they will be very nice to you. IF you see Chinese do not smile at you or something, do not misunderstand. please always remember, we are shy...
Hopefully this help you a little.