This version of the operating system was released in 2005: It's 7 years old at this point, and I'm guessing the machine is just about the same age. With 1 GB of memory, you really won't be able to upgrade much more than one operating system version to OS X 10.5 or maybe 10.6 (the current version is OS X 10.8). Your technician can help you with that. But most importantly, before you take it anywhere, is to back it up.
You should make a good backup copy of your computer's hard drive. Time Machine, Apple's built-in backup software, didn't exist in that version of the operating system. Instead, look for third-party solutions like Superduper or Carbon Copy Cloner to make a complete operating system backup before you take your computer in for any sort of repair or upgrade.
You'll also need to consider adding some memory to your system. One gigabyte of memory really isn't enough to run any modern operating system. These days, 2GB is the minimum required and 4 would be a lot better. Memory is cheap, so go for it.