Hi,
If that is all you plan on powering you can probably do okay just charging off the alternator. The best way to do that is a continuous duty solenoid. You run a 4 gauge or bigger wire from the starting battery to it and then another from it to your house battery. There's another connection point for power from somewhere that only has power when the vehicle is running. It connects the two batteries when the vehicle is running so both get charge from the alternator, but keeps them separate when the vehicle is off so your starting battery doesn't get run down.
As for solar, my advice is always to get as much as you can afford. You usually add to your power needs as you go so more is always better. Having said that, 100 watts or more would probably be more than sufficient with supplemental alternator charging for what you need now.
Hooking up the solar is actually pretty simple. Mount your panels in the way that works best for your vehicle. There are lots of good ways to do that. Mine are on a rack I built onto the ladder rack. You need to mount a solar charge controller somewhere inside of the van. I recommend getting one with an LCD screen so you can see better what's going on. Makes it easier to keep track of battery state and how much charge your getting.
There will usually be three sets of screw terminals on the charge controller. One for battery, one for the solar panel, and one for load. Always hook up the battery first. Use the largest gauge cable that will work to get the best power transfer. Once you've verified the connection is good, then you can connect the solar panels. If it's a small panel, it won't hurt to just connect it. Big panels produce a lot more power and can be damaged by sparks that cause short circuit like current flows for a moment. It's always a good idea to cover big panels with a blanket while you're connecting them to the controller. That will keep any sparks from happening.
The load connection is optional. The controller can usually control the load to some extent and will shut it down if battery power gets too low. The load size usually can't be very big though. It's good for a single item like a refrigerator or maybe your tv or lights. In most cases you will want to use a separate fuse panel wired directly to the house battery to connect all your loads.
Hope this helps.
Patrick
