Rear motor mount on '86-89 Accord - how hard?

[LeeH]

I've about got my '89 Accord fixed up well enough to sell. After replacing the front motor mount there's still some vibration (felt in the steering wheel) at idle when in drive. The rear mount for this car is only about $35, but I can't find any details on what it takes to install one. I'm a little concerned as you can't even see it! My knuckles are just healing from installing the front.

Is there a way to verify with 100% certainty that the rear mount is bad? If it is bad, what's it take to replace? If it's not bad, what else could be causing a vibration at idle? Other than the vibration at idle the car runs and drives great and is in super condition cosmetically. If I bought the rear mount I'd have $2100 in the car (and more hours than I'd like to admit to). I'd like to get top dollar for the car when I sell, but think that will only happen with a smooth idle. The previous owner spend almost $3000 having a remanufactured engine installed, so I think it should be attractive to potential buyers.