You shouldn't need to true up your wheels even annually. Unless you hit something pretty hard, they are very stable if assembled correctly the first time. It sounds like your wheels weren't done correctly in that spoke nipples shouldn't just rattle loose. Normal practice is to put spoke prep on the spoke threads before threading on the nipples. Over several days this prep stiffens up acting something like removeable locktite. The nipples stay where you put them this way. I've built a handful of wheels this way and didn't need to true them unless something 'bad' happened.
What are the rest of the tools in your bike shop like? Are you equipped with decent tools for all the other bike tasks you might need to do? If so, go for it as a personal learning experience. Otherwise, I think your money is better spent on more good quality tools and have your LBS rebuild and true your wheels.
BTW - I've trued all the wheels I've built on an entry level trueing stand. I'm sure a pro level cyclist could telll the difference, but they were round and true for my purposes.