Shawn, I am a hobbyist who enjoys studying WWII, and sharing history/research info with other novices. Until you receive a response from an expert researcher, or until you secure the services of a professional, here is some info you might be able to use. Some are resources I have used researching my own family, others are those I have only read about, or found online. Please be sure to verify all to your own satisfaction.
You should be able to get his personnel record through the NPRC in St. Louis. (They had a disastrous fire in 1973. However, they indicate that Navy Dept personnel records - which would include Marines - were not affected.) Info on that resource can be found at this web page: http://www.archives.gov/st-louis/military-personnel/index.htmlhttp://www.archives.gov/st-louis/military-personnel/index.html
(You said you had tried to get his records, but they needed "a ton of specific info". You might consider trying again. The experts tell us the success you enjoy at NPRC often depends upon the talent and earnestness of the personnel who field your request.)
You can also send for his Individual Deceased Personnel File (IDPF). As others in this forum have addressed, the info found in an IDPF can be graphic. If you pursue this resource, you should be prepared for that possibility. Send your request to: US Total Army Personnel Command ATTN: TAPC-PAO (FOIA) 200 Stovall Street Alexandria, VA 22332-0404 Be sure to cite the Freedom of Information Act in your request. (The above references "Army" but personnel at this command told me via telephone that they also hold Navy/Marine IDPF's for WWII.)
For a Marine's death certificate, try this contact: Marine Corps Commandant Code M-HP-10 Headquarters Marine Corps 2 Navy Annex Washington DC 20380-1775 Phone 703-696-1177 Fax 703-696-2072
You said he was in the "2nd Marines". Strictly speaking, that would be the 2nd Marine Regiment, one of the infantry regiments in the 2nd Marine Division. Is that what you meant, or did you mean he was in the 2nd Division? The distinction could be important. To find "possible fellow marines who served with (your) uncle" your best chance may lie with the division vet association. This would be particularly true if you could identify his unit to a lower level (ideally at least company level). To pursue that possibility, you can visit their website, whose address is: http://www.2marine.com/main.htmlhttp://www.2marine.com/main.html You will notice there you can access their newsletter, "Follow Me". When you access that newsletter, you will notice it has a "department" entitled, "Recon Missions" where, it appears, requests such as yours can be posted.
I hope you can use some of this. Good luck with your search.