OK, if you are a total novice like me and just starting to get to grips with having a van... sooner rather than later you're gonna need to do an oil change... yes, to most of those on here it's not exactly news, but we gotta start somewhere, so...
If you can, get hold of VW Camper & Commercial's Maintenance & Restoration Guide - totally idiot proof advice, it must be, I've managed to come out of it with nothing more than dirty hands and, ahem, some rust in my hair... four quid off their website, money more than well spent!
Step 1. Block the vehicle so it won't roll, get yerself an old wash bowl or something and scuttle under the engine block and av a gander about.... You should see a nice big circular plate with six nuts and bolts around the edges and a bigger bolt in the middle. If it's an older engine then it may not have the big bolt. Fortunately, mine did...
Step 2. Bowl under the plate, loosen the bolt, then unscrew it and watch the deluge of oil as it dumps out to start with and then trickles out for the next half hour.
Step 3. Once most of the oil is out, unscrew all six of those little nuts and ease off the whole plate. You can now see a bit more of what's under there, a gasket (brown ring around the edge of the six bolt ends) and a shiny plate thing with a sort of donut hole in the middle with a dome in it. Take the gasket off, I used a very small screwdriver to tease away an edge and then she fell away with no trouble.
Step 4. Remove the shiny plate with the dome, you'll soon see that this has the filter above the dome, again I used the trusty thin screwdriver to tease an edge and then she loosened all round and out she came. Not so shiny the filter side...

Step 5. Take your filter and your plate and give them a light paraffin bath to clean them up. Meantime, you'll see that there's a second gasket that needs to come off, same as the first, easy does it and yer away.

That brown ring is the gasket, not rust, just dirty.
Step 6. Now that everything is nice and clean and dry and you've disposed of the oil, i.e it's not lying next to you to get kicked over.
Take out your previously purchased "oil change gasket set", mine was about a quid from vw heritage and contained my two gaskets, copper washers for all six nuts and a washer for the big bolt in the centre. Set them out so you know what you're doing.
Step 7. Fit your gasket, filter and gasket back on; all very carefully and making sure you keep them clean and get a nice flush fit over the six bolt ends.
Step 8. Fit your centre bolt and washer on to hold the plate in place whilst you put all the other six nuts and washers back on; snug, but not too tight...


That's it, job done... EXCEPT..... YOU NEED TO PUT SOME MORE OIL BACK IN HER! Handy hint from the ole guide, take the dipstick out when you fill her up, it should prevent any "blowback"...
There you go