I’d like to do a test batch on a recipe I found. It’s an extract kit w/some specialty grain addition. As far as ingredient sizes are concerned, I am assuming that I’d just reduce the amounts relative to the batch size (one gallon in this case). Is this line of reasoning correct? What about yeast? What about boil times and hop additions etc…? Are fermenting times the same as for a 5 gallon? Are there any particular issues I need to be aware regarding small batch sizes? Lots 'o questions but I’m really digging this new hobby and trying learn all I can! The best part about it…you get to consume what you finish 
For the ingredients, yes, you can just scale them down (ie. use 1/5 of what the recipe calls for assuming your translatint a 5 gallon recipe to 1 gallon). Boil times and hop times would stay the same. Fermenting should complete in somewhat less time but it never hurts to let it go longer.
Assuming the same pitching rate it should ferment in the same amount of time, but it can be hard to measure the yeast accurately. If you’re close though, it should have pretty much the same flavor profile.
Use Beer Calculus and switch the batch size to 2.5 or 1 gallon or whatever. I’ve found it particularly useful especially when the amount of malt extract I want is an odd amount. You can adjust it accordingly and see where your gravities are. Same with the Hops.
Mr. Malty has a yeast pitching calculator that will tell you how much yeast you need to pitch for smaller batches. For 2.5 gallon, I still use one vial or package. I don’t have the links handy at the moment, I’m at work and they’re saved on my home laptop.
Edit: Yes, this is a wonderful hob… er… obsession. I love doing the smaller batches because I can make more varieties and have a case of each, rather than two cases of something. Plus, smaller batches let me do full boils, get the most from the hops.
This is what I’m practicing right now. Even made a little 2.5 gallon mash-tun. I’m about to bottle two 2.5 gallon “test batches” and sure there’ll be tears when I drink the last of them! 
When I hit on a recipe that I really think is outstanding then 12 gallons will be made by scaling up everything in the recipe. Got tired of 12 gallon test-batches. ;D
One more question with this. I’m assuming that doing a boil this size will result in a lot evaporation, correct? If so, do I start with more than a gallon at the beginning or top it of with clean water after the boil?
i pretty much only brew a gallon at a time now. mostly lagers so i still do a decent amount of yeast at pitching, though sometimes lazy and just a pack of wyeast munich for a gallon works. then save the slurry. i measure my hops in grams and adjust the utilization equation a bit. since i use lager yeast and cool temps, i still let it go for a few weeks before even checking gravity. i am actually planning a lager chamber on my workbench where i can keep 4-5 one gallons at a time. planning small kegging operation next
If you can start with more and boil down. Expect around a gallon per hour evaporation.
that’s what i lose, about a quart every 15 minutes