Soldering isn't hard. Just get a decent Soldering Station (I have a Hakko 936) and make sure that when you cut your batteries wires, you don't short them by accident. You'll be surprised to see the spark if it happens (with li-pos). Ni-MH aren't that bad. Also, make sure to tin your connectors first, then heat your connectors to prevent cold joints. Don't heat too long or your plastic will melt. You should solder with a second connector connected to the one you are soldering, it makes them looser and easier to plug\unplug afterwards.
You can find some soldering tutorials on youtube, search for some audio cable soldering tutorials, it's the same principles.