The short answer is yes.
The upgrade will depend partially on your hosting plan and server configurations. I've upgraded 3 of my sites with ZERO issues. One of my sites goes funky trying to jump from 5.3.3.1 to 5.4.x.
That being said, the best thing to do is make a .zip file of the '/concrete' folder of the version you are updating to. This is not the whole CMS just the /concrete folder that contains the concrete5 core. Upload this zipped file to your server in the folder where you concrete installation is. unzip this folder and it will automatically over write the /concrete folder that's there. Run the upgrade script by going tohttp://www.yoursite.com/index.php/tools/required/upgrade...... .
This should upgrade your site without loosing any of your information. If your host uses cpanel this can all be done from cpanel's file manager.
making a back-up of the site is a good idea as well.
cheers