There is a huge difference between custom and universal plugs, primarily in the area of sound quality. Best way to go is the ER Series Musicians Earplugs, offered by several manufacturers. The are based around the ER Series filters, developed by Etymotic. These are amazingly flat filters, eliminating the muffled/veiled sound quality from any OTC hearing protection. They are available in -9, -15 and -25 dB strength; your audiologist will help determine which is appropriate for you.
I recommend Sensaphonics, as theirs are made from soft-gel, medical-grade silicone -- the most comfortable for long-wearing situations. Cost is $150 plus the audiologist visit -- which you definitely need as well. Sensaphonics Golden Circle audiologist network is also recommended, as they are trained specifically in working with IEMs.
http://www.sensaphonics.com/?p=331
Regarding hearing loss: it's usually subtle, slow and progressive. If it's exposure-related, smart listening habits can help a lot. The important thing is to get a baseline hearing test, then get retested annually. (You have your eyes and teeth checked annually; why not your ears??)
The apparent dearth of knowledge on hearing health on hi-fi sites continues to amaze me. Seems like people who love great sound would want to optimize their ability to hear it, long term.
Anyway, congrats on deciding to do something about your situation. And good luck!