Yes, there’s a dictionary:
You can buy it and learn Klingon using it. How easy it is to understand depends on you. The greater your background in linguistics and/or learning languages, the more familiar you are with agglutinative languages, etc., the easier learning Klingon will be. Some people will find Klingon to be a relatively easy language to learn. It’s completely regular and has a complete if minimalist grammar. Some people will find Klingon very hard. The word order is more-or-less backwards when compared to English and most European languages, and the language does the bulk of its grammatical work through prefixes and suffixes.
Either way, if you get stuck, there are resources available to help, not least of which is this very section of the KLI website. The folks here are very friendly and quick to answer questions.