hifi engine

GX-707 Value ?

I`m new to this vintage sansui stuff so excuse me if I`m doing something dumb. I just got a Sansui GX-707 rack with an A-707, T-707, P-L40, D-99D, AT-202 and a RG-7. It sat for along time so it was dusty. I clean it up and it seems to work ok except the play button on the left tape is stuck and the volume s;ide is scatchy. It pobably just needs a good cleaning but I`m not exactly sure of what I`m doing. I see on ebay some of this stuff is worth good money and I don`t want to mess it up. I collect old toys and I know cleaning things the wrong way takes away rhe value. There`s a guy at the fleamarket that deals in this stuff but I know he will lowball me to make money. I just need a value so I can deside what to do with it. I don`t want to mess up something someone might really want. I know how mad I get when someone ruined something I`ve been looking for by not knowing what they were doing. Thanks