Dell Oxpcg3 wireless card crapping out

Hey everyone! So Ive had the Dell OXPCG3 for about 3-4 years now without any problems. I didnt really notice until recently that my internet is super slow. I have Comcast's top tier internet plan, I bought a new motorola modem and netgear n750 router which both have high ratings. I used my wifes macbook in the same locations I was having the wifi speed problems and its running super fast. I did several speedtests with both comps side by side in various parts of the house and the mac is reading over 50 mps and my dell never goes above 25. I then connected the laptop through ethernet and it was super fast. I am convinced its my dell's wireless card. It has the intell centrino (r) wireless (n) 1030. I want to upgrade it but was wondering if you guys had any suggestions? DO you know if the laptop case would accommodate a half or full size card? I was thinking of the Intel Centrino Advanced-N 6205S but wanted some advice. The laptop i no longer under warranty so I will be doing this myself. Thanks and sorry for the long read.