Ok, sorry this is my first post. But felt compelled to answer OP's original question.
First, you mention a shop. What do they sell? Is it a vaping shop? Or is it a smoke shop with vaping supplies? Now for my personal experience, I love my setup and I'm about 10 days in. I knew the gas station e-cigs to kinda suck since everyone I've known that tried them has gone back to regular smokes within a week of getting thier kits. Blue, nJoy and the disposables all tend to have a wierd taste and dont hit or feel quite right. I even tried my brother's nJoy and knew that wasnt for me.
A friend of mine clued me in to a local vape shop. As in, that's all they do, only batteries, kits, and cartos/clearos, etc and juices available here. Not only that, everybody in the shop is incredibly knowledgeable and helpful. I asked a bunch of questions and even got to try multiple batteries and setups and juices before even mention was made about cost.
That being said, I purchased an e-Go kit, 2 standard 1100ma batteries, 2 T3 cartomizers, 2 backup replacement coils, wall plug and usb charger kit. The guy showed me first how to fill a tank, and walked me through the process. He also stressed not overtightening anything, but made note that the carto should be tight to prevent leaking.
24 hours later I was back in the store with a leaking problem. He inspected and saw that it was just a wick that was installed incorrectly from the factory. He fiddled a bit and tried it out again and fixed the leaking issue. And a week went by and I found that a certain flavor vaped heavily while others werent doing the trick (24mg - 18mg nicotine levels) So I went back and asked what was going on or how to tweak to get that pleasing vape on the other flavors.
Found out that I was overtightening the cartos, and essentially sealing off the flow of juice to the wicks; which dried out the wicks and prematurely burned the heating element. So got some replacements and loosened things up and all is good.
You didnt go into details here on what exactly happened so I cant say with any confidence this would work for you or your friends that you are helping out - however, Im finding that any replacement of carto to change the juice or even just to refill the tank requires me to tweak it a bit to get it back to a "right" flow and proper vape.
Another question that wasnt asked or even implied in your post; how were you carrying your equipment when it started leaking? If it was in your pocket, i'd be surprised if it didnt leak on you. I have yet to keep my e-cig in my pocket for any longer than needed to use both my hands for something; equivalent to setting it down somewhere. When I'm done, I place it in my case and put the case in a pocket or backback. Another one of those things that you have to get used to. Just imagine you have only a few loosies in your pocket you don't want crushed. (They're probably more durable than that; but that's been my attitude thus far, and haven't had any leakages other than mentioned above which was defect, not abuse)
As for many others talking about complexity of e-cigs vs smokes; they're the same. Your battery is your lighter, juice is your smokes. You always make sure you go to the store and buy enough smokes to last until you next need to go to the store, right? Planning on camping for an extended weekend? Get 5 packs instead of 1 "just to be sure" The only real difference here is you cant bum equipment from fellow users like you can with smokes. Backups are a necessity for that reason, so go with the 2 battery kit, make sure you have plenty of juice - from my experience, I always have at least 3-4 full 3ml cartos on me at all times. If I'm out of juice that means my bottles are empty and need to go to the store; still have at least 9-12ml left to get me to the store.
sorry for the long-winded post, hope it helps shed some insight.
-- vaping is going to be a billion-dollar industry in 2013. There's going to be a lot of investment and innovation in the next few years and that will bring us better-designed, easier-to-use, more reliable equipment at lower cost. I'm amazed at how much has changed since I ordered my first Volt last year. 
