You have to have interface gear and JungleFlasher App to know what firmware is dropped to your dvd drive.
If you were playing games of late 2012 and early 2013 just fine ... you probably have LT +3.0
If you are slighty tech savvy and a quick learner ... you will be able to pick up the process
Slim drives also offer a higher degree of challenge
The other option ... if you live in or around a major city, there are generally those out there offering Flashing service for 360. Craigslist and so on
Since you have the update stall with the new Dead Island ... guessing your console dashboard is 15774 or 16197. It just needs to go to 16203
This next option ... NOT HIGHLY RECOMMENDED .... you can take the update from the Dead island game. This 16203 update may not wreck the custom firmware.
Wait for others to clime in on that. Not certain is 16203 update has been deemed 'Safe'
If you want more input from me - let me know