Installing or upgrading the various Intel wireless adapters by end users is not supported by Intel. There are many reasons for this. I recommend that you review the information at http://www.intel.com/support/wireless/wlan/sb/CS-031167.htm and http://www.intel.com/support/wireless/wlan/sb/cs-006006.htm.
Specifically the Intel® WiFi Link 5300 and the Intel® Centrino® Ultimate-N 6300 have the same electrical requirements. However the 5300 comes in both a minicard and half minicard form factor. The 6300 comes in the half minicard form factor only. Some laptops do not recognize the half minicard adapter. Although it may appear to fit the adapter may not work with the laptop.
The Intel® Centrino® Wireless-N 1000 does not support 5GHz or 802.11a. Both the 5300 and 6300 support 5GHz. If you are looking to replace the 5300 and need to use 5GHz this would not be a good choice.
Another point I need to mention here is that many OEMs prohibit the replacement of the wireless adapter and will not recognize any adapter other than the one originally installed in the laptop. This is true of Lenovo. You will need to contact them to replace the wireless adapter.
Intel Customer Support