downloaded 6.4.6 but haven’t installed. worried that it might corrupt my files in version 6.1
6.4.7 is the latest Stable version and should be good for important work. Don’t use the Fresh version, currently 7.0. for vital work
I haven’t had any problems with old OOo or GO files being rendered differently, except where I hadn’t installed a previous font. The single spaces in .rtf files (often given .doc extension by non-MS & non-LO/OOo programs) are rendered differently which might be awkward initially.
Sometimes, the programs themselves can behave oddly due to corruption in the User Profile, but this isn’t your data files (except Templates). Backup (copy the User folder and sub-folders) your user profile in case of problems. If necessary, you can restore individual folders such as user dictionary, Autocorrect, templates, etc.
I have found upgrading generally to be smooth sailing. Cheers, Al