Travelling to Tokyo for the first time in January, advice please?

Question:

Two of my best friends (ages 20 & 19, I'm 21) will be travelling to Tokyo together from January 11-20.
We chose to stay in Shinjuku, seeing as that seems to be a central location.
We have a general idea of what we want to explore (temples, nightlife, fish market, Hakone hot springs, etc) but I would really appreciate some advice!
For example, how cold do you think it will be? I'm flying to the Philippines for 5 months as soon as I finish my vacation in Japan so I'm going to need help packing my bags... haha
As for nightlife, which areas should we stick to?
And for temples, I know we want to check out Meiji and Akasaka temples but are there any others we should check out?
Foodwise, I'm not really worried because I'm sure there will be plenty of options available..
My only other real concern is the nightlife.. will we have a hard time finding places to go since one of my friends is only 19?
If there's anything you feel I absolutely must do/check-out, please let me know! The same applies if you have any tips for noobs like me haha
I'll have about $1,000-1,500 for personal expenses during my nine days there.. should that be enough?
I really appreciate it, thanks!

Answer:

It won't be balmy, that's for sure. Expect the 40s F or a few degrees above freezing for Celsius.

Take a good digital camera and if you can a camcorder with you. There is so much to see, but a few places to see are:
Harajuku/Meiji Shrine on a Sunday to see the bizarre fashions
Senso-ji Temple in Asakusa - one of the famous temples every tourist goes to see
Odaiba at night for a real trip - try the ferris wheel and don't miss the Statue of Liberty and Venus Fort
See Love Hotel Hill in Dogenzaka near Shibuta Stn. at night for something uniquely Japanese
Tsukiji Fish Market at the crack of dawn.
Akihabara for the electronics.
Shinjuku and Shibuya at night for the endless lights and neon.
Ginza for the overpriced shopping.
Yasukuni for a real experience of NIhonjinron.
Tokyo Metropolitan Gov't Building in Shinjuku (better view from the top than the Tokyo Tower, and
all free!)
Roppongi for the ex-pat environment

Better still, get out of Tokyo when you can and take some day trips to Kamakura, Nikko, Hakone, and the Fuji 5 Lakes.
And to save money you can get a Tokyo subway day pass for all lines for about 1000 yen.
See www.jnto.go.jp for other info, and for some places to stay, try
www.wix.com/astroflight/accommodations