I have a late 2009 iMac running Mavericks (2TB HDD and 12GB RAM) which is now very slow. I want to do a reset and restore from a Time Capsule backup. Will this help if I restore all previous data and settings ? Is my (extensive) data safe ?

Over time my iMac has slowed down considerably. I was hoping installing Mavericks would help "clean" it but I don't see any improvement. I am considering doing a factory reset and then restoring from a backup on my Time Capsule but will this just restore the same issues I had previously ? I have a lot of data from iTunes and Aperture I want to restore (I have backups on the Time Capsule for this data) and want to ensure this can be restored safely.

Having never done this before I would appreciate guidance so that the performance improves and I get all my previous data / apps etc restored.

Thanks !