Hey MAX,
For hardware I would recommend a 2800 router.
For your incoming E1 you will need a MFT (multiflex trunk) that includes DI (Drop & Insert).
Here is a link that will help you out:
http://www.cisco.com/en/US/customer/products/hw/routers/ps259/products_data_sheet09186a0080091b9c.html
For your outgoing Serial you can use either a WIC1T which gives you a one standard DB-60 connection or a WIC-2T which gives you two Smart Serial connections.
On your E1 just create 2 time groups. 1 for all the slots that are coming in, the 2nd for the 10 slots you want to send back out.
To bridge the 10 timeslots, use the global connect command. To view the options use the question mark.
(i.e. router(config)# connect ? )