Blown Seal, just replace the seal?
 

Can you just open the engine and replace the seals?

what type of seal?

if its an apex seal.. then yes, i do believe you can. but most people change the rotor housings as well, since the broken./cracked seal proabably scratched up the housing. check to see if the housing is still in spec. if it is then ur good to go. new housings will insure good compression though. but they run about 500 a pop

in theory yes if you mean the coolant seals, but if that is what you are going to do, make sure you keep all the rotor seals in the the same spot when putting it back together. I wouldn't advise this though, as you will probably just have to do the whole engine anyway.

pull the engine apart, i would never assume its just 1 seal, because your most likley gonna run into more prolems as you take it apart, if it was an apex seal it could have taken out your rotor and housing, but if it was a coolant seal you could get lucky by just replacing that

Reallly depends what seal your talking about,

See this motor only lost 1 seal ( well 1/4 of the seal ) and look what it did

http://img180.exs.cx/img180/372/dsc013806ua.jpg

SO you would have to pop her open as stated above then find out what needs to be done.

That looks just like the rotor I had in my blown engine. It destroyed the rotor housing too. To the original poster, you will need to tear it down to asess the problem, but plan and budget for the worst case scenario - i.e. full rebuild with the possibility of damaged parts.

my rear rotor looks like that but the top corner of each apex is gone. i bought it blown up and that what i found. It had been ran ALOT after the seal went.

i ran about 3 years with a broken seal in the rear rotor :)
car was crap, but the seal broke in place, didnt hurt the housing or the rotor

then i had it rebuilt and was blown away by how the car was SUPPOSED to drive :)