my thoughts... a DVD copy of the 8mm film is going to be DVD quality at best unless they can extract a HD version (something to ask before getting it done). A frame taken from a DVD will be the DVD resolution... not great. A HD source will be 1920x1080 at best, DVD most likely 720x480 (something like that) in a NTSC world. Making a print from that will be bad at best, but more likely to be terrible if you want it bigger than a postage stamp! looking at the actual size of a frame of 8mm (4.8 x 3.5mm according to Google) then scanning it at 4000dpi with a film scanner would yield a 755x551 pixel image... about DVD quality!! (although the quality of those pixels might be better depending on the scanner). hmm thought it might be better than that. Enlarging 4.8x3.5mm of film optically, if my calcs are correct, a 10x8" print would be like marking a 46" enlargement from a 35mm neg... that's not going to look good! Taking a macro shot of the frame using a digital camera might be the best way to get the resolution needed for a decent sized print. What this shows is that moving images don't need to be high resolution to entertain!
Any method is going to very dependent on the quality of the frame on the 8mm film. A better likeness might be obtained by one of those guys that sketch charactertures of you at tourist attractions...