my car sounded very bad and upon raising the hood, noticed a spark plug had blown off. When this happened the steering and brakes got hard to use.
Call a wrecker and get it hauled to a good shop.
Get an opinion on if the plug simply needs to be screwed back in. If this apprasial says that screwing the plug back in is not good enough ask what type of repair (if any) will make it so that you can be reasonably certain the plug will stay in place. If the shop says that no repair will make it so that it is reasonably certain that the plug will stay in place ask what they recommend. If they recommend that the head come off and go to the machine shop,or worse,that you need a different engine,be sure to post back before you give the OK.
Lets take getting the plug back in first before we deal with the steering and brakes.
Are you saying that a spark plug wire had “blown off”, or that a spark plug was blown out of the engine?
In either case, your power steering and power brakes getting hard to use was because the engine stalled, presumably because of the spark plug problem.
I went with the plug blowing out rather than the wire comming off as the sound of an engine that is operating with a plug blown out will cause someone to cite that noise as the reason they finally raised the hood. A 4 cyl that is running but with a dead hole will still produce enough vacuum to operate the booster and many 4cyls will run on 3 cyls without stalling. My only theory about the steering is that perhaps when “the sparkplug shot out like a rocket” if blew the power steering belt to bits.