Need to reset and wipe my phone to get rid of a problem but need some help

So I've got a problem on my iPhone 5 with the 'other' section of my storage being mysteriously taken up by 9GB of nothing from what I can gather and apparently the only real way to clear it is to wipe my entire phone back to factory settings. So if I do this, which is a last resort but no one has been able to give me any other answers on how to deal with the problem, what things should I be aware of before syncing e.g. contacts maybe being wiped, so write them down beforehand to add again, etc. and also will all the info/prgress in apps I've put in over the past year be completly wiped or not?