I have done this repair before by cleaning back the broken part, building it up with brazing rods, re drilling and fitting a solid type thread insert like the Wurth Time serts. Its a fairly big job and you will need to remove the engine but not as big or expensive as replacing the block.We have had to do it on the 4 cyl, V6 & V8, they are just a very crap design, a bit like the rest of the engine!!