how do you guys know for sure the seal is installed correctly? i've been told that it can look fine from outside but it can be rolled on the inside edge..........would a little oil prevent this? or is there a special tool

 

Yes, most definitely lube up the lip of the seals to prevent dry start tearing of the seal. One trick to preventing the spring from popping out if you accidentally roll the lip is to pack grease in the back side of the seal. Take special care that you're tapping the seal down flush. They can be tricky so have some patience.

 

had no idea the seal had a spring in it