WElp. I think the 13B-REW rebuilds run about 2 or 3 grand from a reputable shop. And they can port the motor for you while they have it apart. Then it'll be like brand new 7 all over again, except with more balls.
check out
http://www.pineappleracing.com/ for one of the few really good rotary shops taht can rebuild it for you. I don't have a list of all the builders on this computer, but i'll put it up in a couple days. Also you can check out ww.nopistons.com for more 7 information. Another one is
www.rx7club.com, but becaureful with that ones, its a highschool forum if you know what i mean.