Need some help please guys.

My 53 plate mondeo tdci has started playing up. the problem is that after driving perfectly home we went to go back out about 30 mins later. It wouldnt start! It spluttered and coughed but nothing. the glow plug light was also flashing. does this mean the glow plugs need changing?

if so, will this be expensive or is it an easy diy fix?

cheers