My best advise for changing strings is to try any set you want that is appropriate for the guitar. Try 9s, 10s and 11s if you want. The thickness and composition of the strings can have a huge effect on the guitar, especially an acoustic. That wood is a vibrating! Next is get proficient at adjusting the truss rod and action/intonation at the bridge. There are a million videos on youtube for instruction. Unless you start cutting or drilling or sanding, then you really can't hurt anything that badly. All guitarists should learn to to a basic set up on their axes. It will save you so much time and money and you will always be able to make your guitar play great and in tune after messing with strings.