Be a "can do" guy. Don't say "no, I can't do that" when asked to do a task. If you have to research something then say so. If the place is well organised there might be resources you can use anyway.
As fairly recently promoted from developer to a manager I have a comment to the above.
We all love "can do" guys, but only if they really can do. If your you are already fully booked please learn to say so. If you over commit you either
- need to work a lot of extra hours in order to complete your tasks or
- fail to deliver work on time
While the first is mainly a problem for you initially, it will most likely hurt everyone in the long run when the quality of your work starts to drop.