Josie, I have a Ram 2500 with a short bed. I Tow a 31' Eagle 285. with a Valley 16k sliding hitch. On short beds the sliding hitch is recommended, but I have never had to use mine yet. There are 5er's out there that have the front end designed so that a slider supposedly is not needed. There are also hitches such as the Pull-Rite that automatically slides if needed.
Soooo....depending on you budget and 5er design. A slider may not be needed. Or, go ahead and get a slider. You may need it for your next 5er. The brand/type you get is where costs come in. I paid around $1200 for my Valley set up. Pull-Rite I understand goes for around $2500. You can always look for used.
2010 Jayco Eagle Super Lite 28.5
2007 Dodge Ram 2500 5.9 CTD