Veritas works very well, as it is "the state of being true". You could go with certitudo, but as you might be able to tell, it has more to do with knowing you're right than with what you're saying being predicated on some sort of objective and verifiable truth, if you catch my drift. Basically, veritas (ueritas if you wanna get really pedantic) is about truth in an external and objective sense, whereas certitudo (so, the pedantry is in making the u's and v's the same; some pedants like to get as close as possible to the way it was inscribed and will write creditvdo) is about truth in the mind of the knower.
For knowledge, you'll want a noun, rather than an adjective. Scientia is traditional in college mottos and with very good reason: it has by far the broadest definition. It is derived from sciens ("knowing"), the present participle of scire ("to know"). Cognitio is whence we get the words cognition and metacognition, but it doesn't mean knowledge so much as it does idea. Thus, it might work for your purposes. All the other nouns that I'm seeing are restricted to concepts of skill or illicit knowledge, or recognition as opposed to knowing, if that makes sense.
Service, on the other hand, is the most interesting as there are many shades of meaning to choose from. I like beneficium (literally meaning, "to make a good") and meritum (literally, "that which is earned"), though you could also choose officium, opera, or ministerium. These three have connotations of duty, work, and occupation, respectively. You can always use munus, which does connote the giving of gifts but which can also imply things like bribes. My personal favorite, however, is pietas. This is the word from which we derive the word piety, but to the Romans it had none of the religious significance we give it. Rather, it referred to the development of a character whereby you kept your word, followed through on your obligations, gave back to those who had given you (quid pro quo IS a Latin phrase, after all). Taking this original sense of the word and backing it up with more modern philosophical notions based in the idea that we're all in this together, and ecological understandings of interdepoendence makes my brain happy, at least.
I hope this answer doesn't come too late!
