Fairly easy to do, cost about 1400 plus or minus, if you have a controller in the vehicle. No controller necessary for surge brakes. Dexter, BrakeRite and HydraStar are the accentuators and run from $ 800 to $1100 for just the controller. You need the lock out, battery and some new wiring. Most disc brakes can be converted, but some are not suitable for the higher pressure of the electric over hydraulis--and then the controller in the $400 range. Up to $2000 if you need all of the parts.
I usually run all new lines unless they are all metalic and then new wiring and new brake cylinders. Cylinders have to stand pressure of 1200 PSI +/- depending on brand of pump. Some trucks and a few SUV's have the proper wiring and control already there. My 250 Ford had all of the necessary wiring and controller, but it came with the heavy duty and 5 th wheel towing package.
I order from E Trailer and have done 3 trailers conversion. It is worth the cost in my opinion to have better control. If you tow the 25 and any C Dory above that in length (over 6800 lbs) in Canada it is obligatory--have to be able to apply the brakes from inside of the tow vehicle. Either electric drum or Electric over hydaulic is necessary for that function.
