if you have the whole thing on ONE mono track it is virtually impossible to remix individual instuments. some very very good sound engineers specialized on frequency-mixing can - to a certain degree - improve the sound of a recording like this. but as a basic rule in recording: there might be tonns of fancy recording/mixing tools - but you cannot turn sh*t into gold even with the best hard/software.
i´m not saying your band or your music is crap since i havent heard it. dont get me wrong. when you are after a good recording, then focus on a clear and not too overloaded arrangement. every instrument/musician needs enough space to come to live on a recording. keep this in mind when writing/performing/recording songs. and the better the input, the better the result. alot of musicians think "well - the sound of my instrument isnt that important - the sound engineer can mix it and it will sound great". - WRONG!!!!!

however - back to your problem. what you have is probably onle level above a bootleg recorded with a walkman. ditch it. or keep it in your memories-album. for your next gig, try to get someone who can provide a well equiped computer or harddiscrecordingstation that is plugged into the mixer and record every instrument on a seperate track. then you wont have as much problems with the mix.