What is the infected file name, where was it found e.g. (C:\windows\system32\infected-file-name.xxx) ?
Check the avast! Log Viewer (right click the avast 'a' icon), Warning section, this contains information on all avast detections. C:\Program Files\Alwil Software\Avast4\ashLogV.exe
The avast Win32:Trojan-gen is generic signature (the -gen at the end of the malware name), so that is trying to catch multiple variants of the same type of malware and is a fine balance between detecting a new variant and detecting something valid as infected.
So there is no specific trojan description.
Save your money you don't need a computer guy, the chest is a protected area where the file can do no harm. With the information asked for we can be more detailed in our help.