hawaii rx-7

hey, last night, while i was under my car changing the tranny fluid, i noticed the block of the transmission had these little spidery hair line cracks barely visible. at first i thought it was just around the super tight filler plug, but upon further examination, i saw signs of these cracks all over the block. i was wondering if they were just cosmetic flaws and superficial cracks or are they something to be worried about. i haven't heard anything about the reliability of the transmission in our cars, so i guess this would be a first. if i can, i'll try to get pictures of it, but till then, it would be really nice if you guys could give me a little feedback.

i'm hoping this is nothing to be worried about, but just in case, would anyone know how much a new tranny cost? and while i'm at it, how much is a 6 speed?

thanks,
hawaii rx-7

ps, at a time like this, some reassurance would be quite pleasant

here's a little info on my car:
it has about 66000 miles on it, i'm the 2nd owner, so i don't really know the history very well, basically stock except of an intake and downpipe, and i'm in the process of completing all the reliability mods. the only race i've done is about 10 1/4 mile passes (no launching, no redlining, gental 6000 rpm shifts and rolling starts)

hawaii rx-7

bump.
my scanner don't work, i'll try again with the pictures later.