Upgrading is a good option, but (as you are) some research to make sure the new hardware is compatible with your motherboard.
Did a quick search and found this, its the same Model as you posted, but the Processor is listed as an i5 which is alittle confusing (and concerning).
Memory (note it does not list a pin count)
Slots: 4 DIMM Slots, Type: DDR3 (UDIMM), Speed: 1600 MHz, Module Type Supported: 2GB/4GB/8GB, Max: Up to 32GB
Integrated: Intel® Integrated
Discrete: ATI Radeon HD8470, ATI Radeon HD8570, NVIDIA® GeForce® GT620
TOWER - PCI: 1 x Full Height, PCI EXPRESS x 1: 1 x Full Height, PCI EXPRESS x 16: 2 x Full Height, MINI PCI EXPRESS x 1: NA
SFF - PCI: 1 x Low Profile, PCI EXPRESS x 1: 1 x Low Profile, PCI EXPRESS x 16: 2 x Low Profile, MINI PCI EXPRESS x 1: NA
By that info, it does look like you have room to upgrade, but the CPU difference in what you posted and whats listed on the site could mean different mother boards, i would not go by that with out double checking.
It might be a good idea to drop a line to Lenovo and get as much info from them as possible before buying any hardware for your current computer.
Good luck to both you.