Fixing your own computer can be a risky endeavor, and is not recommended unless you have extensive experience in the area or have done extensive research. There are many computer repair services available online, and they don't just offer repair services, but may also include other services in the package. Generally speaking, the cost of repairing or upgrading a laptop or desktop computer should not exceed the cost of buying a new one. If you're looking for computer repair services in Melbourne, you can search for them on Google.
When deciding to repair or upgrade your computer, make sure you find the right repair service for you.