Makes sense to go down the kit build road if it means you will be able to sleep at night Rik, don't think there really is a right or wrong way to go about it, you either purchase a ready made machine, buy a kit & assemble it yourself or build it yourself from scratch, everyone's different & what suits one person doesn't suit the next.
Best of luck with the stopping smoking, I stopped for nearly 3 months about 20 years ago. Then I was able to get out the hospital bed & go down to the day room for a fag lol Thought many times since then over the years that I should have just packed in there & then, would have saved a fortune & to be honest I didn't really want a fag when I did go for one, only really did it to spite all the people who had been saying I hadn't had a fag for weeks & should give up lol