1. Do I have to assemble this myself? - this comes already assembled. Just open the box and add fishing line.
2. How far will it cast? - that depends on the weight of your bait, lure, sinker, etc. the more weight, the further it cast.
3. Would this work good on a deep sea fishing trip? - lol no. You might want another pole. This is for heading to your local river or lake and tossing a line
4. Is the cane length adjustable? Yes,it adjust in seconds from 32” to 38”.
5. What pound test line should I use? - ideally, four, six or eight
6. Can I return it within 30 days if I don’t like it? - absolutely E-mail firstname.lastname@example.org for the return address