As the Snooper states, no problem at all for that machine, it has a good low power range.
If however you have never welded car body thickness it may be worth doing a few runs on some scrap first, even at the lowest setting all machines are capable of blowing through and you may have to use the thin metal technique (see tutorials above)
With a van it may be possible to press a lump of steel up underneath the repair to act as a heatsink, copper is the best but anything solid will help.
It will be difficult to stop future rusting in this area, is there a head lining to remove in this area? Most important at all what happens if you set it on fire or damage the electronics etc. sooner or later that seems to happen if you take such jobs on
Frankly without it being your line of daily work its often better and wiser to turn down work on vehicles. I am sure the machine can handle it with 0.8 or less on the spool if you can though