TheKansaiKid said:
I think feelings of apprehension before trying something new is common and healthy, I think you'll have a great time.
Advice that I wish I had been given before I went to Japan:
Don't worry about money too much, never play the converting game of "Holy Crap this pizza costs 30$" Just think of it as yen with no connection to real money and you can relax and have a lot more fun.(I hope either you or your dad is rich)
2 months may seem like a big chunk of life, but time will fly by you'll be home before you know it.
If you and/or your parents aren't wealthy, then DO pay attention to the amount of money you spend -- it takes a period of time before you start looking at foreign currency as Real Money, because it looks and feels different than money does back home. So, even though 'ichi-man en' doesn't feel like a Benjamin, remember that it's still worth about the same.
On the flip side, don't be so miserly that you can't go out and do anything. Sure, a pizza will cost $30 and be tiny, and a 'grande' at Starbucks will be tiny and cost $5, but it's worth it for the experience. Also, go to local, smaller shops, and you'll likely save money over the big chains, and don't forget that combini sell really good, cheap bento for 100-500 yen ($1-$5).
Last but not least, it's always normal to feel that sense of apprehension -- hell, I've travelled a lot, and I'm going to Japan for my first time this summer, and I'm nervous as hell, despite the fact that I've got a lot of support built up for this trip (Japanese girlfriend, other friends in Japan, two years of Japanese study, etc.) Just go there, throw yourself in, and have fun.