Access Point Upgrade to 802.11n & PC card for Sony VAIO Laptop

I want to upgrade my aging (5-6 years?) 3COM Office Connect (802.11b) cable gateway, which requires frequent rebooting, with a Buffalo Technology Wireless-N Nfiniti Dual Band Gigabit Router & Access Point.

Currently the only wireless device is a Sony VAIO Laptop, model PCG-GRT250P with a wireless connection described as "LAN-Express as IEEE 802.11g minP"
 
Does this upgrade make sense, and will adding an 802.11n wireless PC card to the Sony VAIO Laptop improve performance?

Thanks for your help.