Not sure what solenoid you are using, but a 200 amp rated Cole-Hersee has silver-tungsten contacts and should last the life of the RV with moderate use.
https://www.amazon.com/Cole-Hersee-24213-Continuous-Solenoid/dp/B005K2429I/ref=sr_1_1?s=automotive&i...If your existing solenoid has only one small terminal, just connect the existing small wire to either one of the small terminals, and make up a short 16 or 14 gauge wire with appropriate size terminals on the ends and connect the other small terminal to one of the mounting bolts or other suitable ground adjacent to the solenoid.
When tightening the large cables, DO NOT allow the inner nut on the solenoid to turn, ever. Doing so can cause the contacts inside to shift and the solenoid to fail prematurely. Use a second thin wrench to hold the inner nut in its current position.
Charles
2007 Winnebago View 523H on a 2006 Dodge (Daimler-Chrysler aka Mercedes) Sprinter 3500 chassis (T1N). Bought Sept 2015 with 18K miles on it, Prog Ind HW30C, Prog Dymanics PD4645, Coleman Chill Grille, PML/Yourcovers.com deep alum trans pan, AutoMeter 8558 trans temp gauge, Roadmaster sway bar, Koni Red shocks (front & rear), Fantastic Ultra Breeze hood, added OEM parabolic mirrors and RH aspherical mirror, MB grill conversion.
'03 Ram 2500 CTD, 5.9HO six speed, PacBrake Exh Brake, std cab, long bed, Leer top and 2008 Bigfoot 25B21RB.. previously (both gone) 2008 Thor/Dutchman Freedom Spirit 180 & 2007 Winnebago View 23H Motorhome.