Are you planning a lot of dry camping? 99% of the time hooked to shore-power when camping? Residential fridge in the TT?
If you are going to be hooked up to shore power at the CG's there is no reason for going with expensive deep cycle batteries. Unless, you have a residential fridge then you will need a couple batteries.
Personally, if your current battery is still holding a charge, I would stick with it for a few more outings. It is a LOT cheaper to practice on an inexpensive battery than KILL expensive deep cycle batteries. For extending your awnings, slides, levelers (if you have), leave the TT connected to the TV while you care for them... your battery will love you.
Go with the battery disconnect switch first. Below are a few wiring tips, a Digital Voltage meter to monitor your battery (should not go below 12.0 VDC), and where to put your disconnect switch. Oh, keep a digital volt/ohm meter in the TT, you will need it at some point.
There is some battery information on our RVing with SOLAR
2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
MagicJack Internet Phone
2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package
Our Solar Album http://www.jaycoowners.com/album.php?albumid=329