Google is your friend here-look for a disassembly video on your particular gun. Watch the video all the way to the end and make sure you feel confident before you start. You definitely will need a spring compressor. A look at your parts diagram will also help you understand how the gun goes together and comes apart.
Is your Beeman an R series or one of the Chinese models? The R series have more options for aftermarket parts.
A picture of your gun would help.