rydaeb, there is no way to be "totally safe". You can walk into a gun store and the salesman can rook you into purchasing a total dud. Ask the right questions. Record the information. Ask for their PAL number and check it out with the CFO for legitimacy.
I have bought and sold many firearms on the EE and have been very satisfied with the results. In many cases, you may be able to negotiate a bit with the seller/buyer - more so than at a store.
Now, back to the topic at hand. The action I shoot is pretty much dictated by the situation I am in. My answer to the OP's question is kind of complicated.
For shorter distance (under 200 yards) and bush work, I much prefer my 30-30 lever. It is light and compact. My second choice is my 308 due to it's shorter barrel. Oddly enough, my son really likes his M14 shorty to my bolt rifle, due to the decent accuracy, fast second shot and speed of reloading (when plinking or shooting at stumps due to boredom.
For longer distance, wide open country, I prefer my bolt - specifically my Lee Enfield and my Parker Hale (both of which were bought on the EE). I had a BAR which was accurate enough, but I hated the magazine system and pretty plastic on it. The Belgium BAR's are heavier as well, but still have that goofy floorplate/box magazine system. For a semi, I will use my tweeked M14 for shorter (300 yards) stuff, as I use the open sights on it. I used a pump for a while, but it made as much noise as the semi's - which is another reason I prefer a bolt for this situation - as I do not ever walk around with a round in the pipe - ever, mechanical safety or not.
For my truck gun, camping gun and general all purpose - my Marlin 30-30 336W wins hands down. I have never had a jam with it, it is accurate and for coyotes and other pesky varmints, I shoot an awesome 100 grain bullet out of it. For general purposes, I load up the Sierra 125 bullets. I can also load up a 150 or 170 grainer for pesky bears roaming into the campsite. It's a great noisemaker (2 shots) too for just scaring away bears - because the other four in the magazine will mean business. It is also quick to reload. In other words, the perfect solution - as 100 years of popularity will attest to.