Welcome to the board. Nice introduction.
I would go easy on yourself regarding the meditation. 10% of focus is great, the daydreaming will subside in time, as you get into your practice. No need to worry unduly about all that.... keep at it, and you will reap the benefits.
I remember a good book on Buddhism called 'The Buddhist Handbook' by John Snelling. This is well written and clear. It takes you through the historical developments, as well as the doctrinal side of things. At the back, there is a large glossary on Buddhist terms.
Recently, I bought 'A Dictionary of Buddhist Terms and Concepts' which is published by Nichiren Shoshu International Center. It is very good, and has an extensive list of entries (1400), which for a regular sized hardback is pretty good:http://www.amazon.com/Dictionary-Buddhi ... 087&sr=8-1
I found it to be unbiased, and not particularly coming from any one angle or doctrinal view. It also seems cheaper than the other Buddhist dictionaries (25 dollars for a used copy on Amazon).
In truth though, I would probably recommend that you bought a decent book with a good glossary, rather than an expensive dictionary, as it would probably benefit you more in the long run. You can always go to the library or Buddhist center to look through the larger reference books...
Also, online there are more and more resources on Buddhism popping up. A quick check found this:http://www.accesstoinsight.org/glossary.html