Not sure where bog wood comes from, but I am sure that it is treated somehow before it goes on sale at your LFS, so that may be why it is so expensive.
If you want to put rocks in your tank that you find out side, first clean them very well with a scrubber of some sort. Then put them in a bucket and pour boiling water over them. NEVER put rocks in boiling water on a stove and leave them in there! There are small amounts of water/moisture inside the rocks, and when the rock heats up the water inside will begin to raise in temp and give off a gas, and then, BOOOOOM! People have gotten really hurt from boiling rocks. So, just put the rocks in a bucket and POUR boiling/really hot water over them. This will kill off any parasite on the outside of the rock, with the core temp of the rock barely rising at all.
Pest snails? you can remove them by hand/gravel vac, but that would take a long time. DP (Dwarf Puffers) will eat the snails. Other than that, I am sure other members will have some info on removing them. I also read something about putting a piece of lettuce in the tank. The snails will begin to group up on the piece of lettuce, then you can just remove the lettuce, thus, removing the snails.
A test kit is one of the key components in a healthy tank. A basic test kit will test for Ammonia, Nitrite, Nitrate and pH. Different levels of these within a tank can harm and even kill your fish. Most fish die from ammonia poisoning. Why? Because the fish keeper did not have a test kit, so he/she did not know there was a high level of ammonia in the tank. A high level of ammonia can be caused by many things, but it is most commonly caused by an un-cycled tank. Ammonia and/or nitrite present in a tank at or above .25 ppm will cause harm and even kill your fish. Some fish may not show any signs of this, so the only way to know about these dangerous levels is through a test kit.
There are different test kits available today, and the best ones are the LIQUID test kits, NOT the strip test kits. So, if you get a test kit, which every fish keeper should do, make sure it is a LIQUID test kit!
EDIT: Also for the rocks, after you have them cleaned you should perform the "vinegar" test. Put a couple drops of vinegar on the rock, if the vinegar fizzes, then the rocks are no good. This means that the rocks will raise the pH of your water. If the vinegar does not fizz, then the rocks are safe to put in the tank. Make sure they are around room temp when you put them in the tank.
-FHM