Tholliday - Sorry to hear about your grandfather. Let's get this gun up and running so you keep your memories! Yes, the breech plug section of the gun can be removed, but my question to you is why? In a traditional cap-lock muzzle loader there is really no reason for you to remove the breech unless you needed to replace it due to a broken off nipple bolster. Get a breech scraper attachment for the ramrod and scrape the bottom of the barrel if you are concerned about carbon or black powder residue build up. Now as for the "ramrod thimble", they are held on to the barrel with a screw. If you can back the old screw out T/C can send you a new thimble and screw, or you can replace it with one designed to hold a sling swivel.
I recommend you forget about taking out the breech plug, it is not worth your trouble. It is very likely rusted in place and would require heat to break it loose. I have owned a T/C Renegade .54 for 30 years and never taken my breech plug out.
I also recommend you read this - http://www.tcarms.com/assets/manuals/current/Shooting_TC_Side_Lock_Black_Powder_Guns.pdf
If you broke the ramrod, replace it with a fiberglass or aluminum one anyway which I recommend anyway.
Call T/C Customer Service - (603)-330-5659