For 11 years I climbed under my Taco and Fluid Filmed it. When I sold it there was light rust starting on the door sills and tailgate. From the inside rusting to the outside. Had to look for it but it was there. With rust the main concern is areas that you can't see or easily get to. The frame didn't look too bad at least on the outside. Year and a half ago picked up my 19 GX and according to the service history had spent summers up in the Cities and winters down in Texas so hadn't seen salt. One of the main reasons for me buying it.
First thing did was clean the underside and take it in for NHOU Undercoating. NHOU is Fluid Film on steroids for over a year it was creeping UP on the outside of the vehicle. After watching a professional install it and spraying into areas I never thought about I will never do it myself again.
But the guy that did it near me moved back to Pa. so I'm looking for another place to have it done this fall. First year on my Taco I used CF2000 the Canadian snake oil and it was slightly better than FF but got expensive so switched to FF. I feel NHOU or Woolwax are better and stay around longer I skipped last year. Heck the NHOU was still coming out in places this winter. I did a rust test to destruction with several products almost 15 years ago and the CF2000 was just a bit better than Fluid Film. But FF worked as long as it didn't get washed off.
Big R Service Center up by you in Randolph was listed as a Woolwax applicator but they don't have it on their website any longer. Big R does lifts and rear ends they are highly regarded but not sure what they use for undercoating now. Later this summer I will call them and see. I may end up going across the River to Onalaska to
EMN Paint Correction and Detailing. They will do FF, NHOU or Woolwax you pick. For prep work they say they use a air needle scaler, 20 years on ships in the engine rooms I have more time behind a needle gun removing rust than I care to admit. But what about inside the frame and panels? They are also spendy and start at ~$400. But to do it right, may be worth it.
Good luck and have fun with the new rig! Snow is melting never mind the 12" that is supposed to drop starting in a few minutes. Soon I will be running around Mn. Wi. and UP to break clay targets at side by side shoots with double shotguns. Mid Sept. I head to the Sunset Country of Canada chasing birds with the dog then the month of October at a cabin mid trail on the Gunflint. Hope to see you in the North Woods sometime.