their are many different types of isolators, but they are typically super easy to install.
most of the ones i have dealt with take the charging wire from the alt which goes to one post of the isolator, then the other 2 posts on the isolator go to each battery bank (one to the truck, one to your camper)
But, isolators arent usually very cheap (and really, for what they are and what they do its pretty expensive!). alternatively you can just run a power wire from the truck batteries to a master switch in your camper that you can turn on and off to charge the camper batteries. But, this method also relies on your memory to remember to switch it off!
Or... You can use a high amp relay in the line between your truck and camper. Hook the relay up to keyed switching power, so your truck and camper will be isolated unless the key is on (truck running). this i think is your cheapest and best option
2007 Laramie 3500, 4.5" RevTek, 35x12.5 ProComp MTRs, buckstop front+rear, bullydog TD, BD RFI intake, Lightforce 140s in the bumper, 240HIDs up top
1997 SLT 2500, 5.5" fabtech, 36x13.5 IROKs, 5x12s, s300, 4kgsk, inj pump FUBAR