1) As previously mentioned- buy a copy of this book- Whitewater Nepal, 2nd edition, by Peter Knowles.
Note that a lot of the book is inaccurate in the details, though it's still an invaluable source of knowledge, and there isn't a second source in print.
2) I'd contact GRG in Kathmandu for a cheap place to stay, and possibly a boat rental if your'e not bringing your own kit. Maila, one of the owners (husband and wife) is very nice and super knowledgeable. They have moved since the earthquake, so I don't know their new location. I'm friends with them on facebook though, so I can put you in contact if you like.
3) In Pokhara, there is a general "kayak bar," to meet other paddlers, though I forget the name.. It's in my notes. If you like I can dig for it.
4) The bus system is amazing. 90% of them have roof racks that take kayaks (watch the sharp edges, they will slice a boat!). Flag them down. Haggle. Tie on boat. Get inside. TIE YOUR BOAT DOWN YOURSELF! The locals are great at tying down bags, hit or miss on your kayak. Take some extra straps (shredded a spectre throw bag on a roof rack there). Maybe 50% of taxis can also take your boat. The tiny taxi racks can take 3 kayaks without too much drama, if you strap them right.
For runs not on the bus routes, hiring a jeep is usually best. It's not too expensive if you get 4 or 5 paddlers together.
Note that you're going there in the low season. I haven't paddled it that time of year, so I don't know how easy it is to find partners randomly.
If you want specific beta PM me.