Do some 3D Modelling

I have 2 existing .stl models that need to be adjusted. Both had problems when I sent them to the printers, so now I need someone with solid 3D modelling skills to help me to alter them. Part 10: Belt This object is 60cm long, which apparently is too big for most printers. To get around this issue, I want the 'belt' to folded around into a semi-circular shape, while retaining the original dimensions. This should make it small enough to print. I've attached a rough sketch to give a clearer Idea of what I want. Part 2: Standard Cog According to the printer, this 3D model is 'open' not 'closed', which means that somewhere on the model, something is not joined together properly, 'closing' the shape. If an object is 'open', the software on the printer will not allow the object to be printed. So, I either need this model to be fixed 'closed', or redone entirely. This should be a quick and easy job for someone who knows what they are doing. I'll look forward to recieving your bids! David