Engine bolt removal question!

While frustratingly tightening the nuts on the EGR valve, i overtightened the nuts and one of the bolts sheared. However i managed to reattach the valve but now i heve some air leaks from the area. My question is, before i remove the valve again, how hard would it be to remove the bolts from the engine? Could i clamp a vice grip on the sucker and replace the bolt? or would it be so stuck in there that im screwed? Also, would the threads on the bolts be "opposite" so that i would have to turn to the right to loosen?
thanks

 

they should be normal. if you turned it right and it was left hand threads it would back out...

if you cant get it out via vise grips you may need to drill it out and use an easy out to remove it

 

i know its pretty much impossible to say the bolts will come out easy but the space is pretty tight so getting a drill in there and being able to work it will be next to impossible and i dont have an easy out.
Also, would anyone know if i could get the bolts at auto zone or would i have to go to toyota?