Hi,
If the 4WD videos are of US origin they will probably be NTSC not PAL (the system we use in Australia). This means you will need a NTSC compatible player that will output a PAL video signal (a lot do not do this) and then you need to convert that to a digital format via a digitiser plugged into a computer to turn into a MP4. Also the quality of the NTSC videos will be not as good as a good PAL one. And yes, there are digitisers and there are digitisers and you can tell the difference. The ones we used to use in broadcast situations used to cost about $35,000 and then we used a $3,000 VHS player to go with it.
So my advice is if these are irreplaceable videos you really want on your computer, then get it done professionally. Do a Google search on NTSC VHS (or just VHS) to MP4 conversion and there will be someone in Melbourne to help.