Welcome back to the camping world. As far as directories most are online now. Good Sam has taken the place of Woodalls with their directory they sell for about $7 with the membership. About the most complete listing of camping/rv parks is www.allstays.com
. There is no totally complete directory as it is ever changing. You may want to join Passport America which offers many campsites at a 50% discount (with some restrictions) and has a directory that is out of date the day after it was published. You may want to check government sites on www.recreation.gov
and of course each state has state park directories online. You can also get travel information for each state from their travel bureaus and you will get a list of camping locations that are state operated. Some states like Texas have campground owners associations that have directories, theirs is called TACO (Texas Assn of Campground Owners)
If you are over 62 years old you can purchase an "America the Beautiful" pass which does not expire (good for your lifetime). It now costs a one time fee of $80 as of September 2017, plus shipping ($10) or you can go to their website (https://www.nps.gov/planyourvisit/passes.htm
) and find a government park near you that will issue the pass onsite. The pass gives you free entry to most National Parks (contractor operated may not be totally free), BLM grounds and other government owned property and gives you a 50% discount for campsites like Corps of Engineer campgrounds (my favorite). TVA and a few states will also honor the pass.
As for the Good Sam trip planner. It is not bad and lets you change routes to suit your needs. As for using it to find campgrounds it is very lacking in being complete. It promotes Good Sam discounted campgrounds and some state parks but is not the best. One of the best trip planners is www.rvtripwizard.com
which has a $40 annual fee for use.
You haven't said what brand of TT you have but if it is a Forest River product you can join FROG (Forest River Owners Group) free to join, http://www.forestriverfrog.com
and check the Events dropdown for fun Rallys to attend. Some other manufacturers have owners groups also.