I live full time in a small RV (8.5" camper on the back of a truck).
I have also lived the last 20+ years on a sailboat (never at a dock, always on anchor) 3 to 8 months at a time.
This might get long, I hope to help you, and hope you know that I have real experience in this subject. Also, I am frugal and not going to refrain from recommending anything too expensive.
First, I will point out a often overlooked flaw with the Sprinter van. It isn't 4wd. This may not be a problem for some, but at the price they command, it is a problem for me. I spend 2 months a year in the mountains hunting, and winters in Baja on the beach, in sand. No vans make it past the first mud or through the sand. Now, 4wd isn't perfect, but in mud, snow, ruts and steep areas, without it, you don't go. Every year we finish up hunting in a snow storm with 12 miles to get out, across slippery mud and muck. Chains all around is required and so far, in 28 years, twice we used our 9000lbs winch.
For driving on improved roads, the Sprinter is great.
I wrote a post here talking about my reasoning that there are other options to look at... let me see if I can find it...http://forum.mrmoneymustache.com/welcome-to-the-forum/fire-in-a-sprinter-van/msg582026/#msg582026
What you are proposing can be done, and available solar power *shouldn't* be the limiting factor.
You can use 3 SunPower e327 panels. (Or the X335/X345 panels) They are 5 foot long, and 41" wide. There will be about a ~14inch gap for the vent.
First, your biggest power drain will be the fridge. This is a terrible type of power drain, constant and basically never ending. You would be WAY ahead to use a propane fridge. But, fear not, you can use an electric if you choose. I would recommend a marine 12v fridge. This will set you back as much as an RV propane fridge, but when going electric is going to be a *MUCH* better choice than a dorm 120v $79 costco special.
We have a norcold with a custom built insulated box. It draws 25 watts and runs 24/7 (it is in a hot environment, night time lows average 85 and daytime is 93). A bit like this, http://www.westmarine.com/buy/norcold--universal-voltage-marine-refrigerator-black-2-7-cu-ft--14000830
Assuming you use something like that for refrigeration, I know that one 327w panel will run that just fine with 2 golf cart batteries. In decent sun.
So, wire each panel to a 30amp Tracer MPPT charge controller (eBay $109) these have been working great for me.
Start with 6 or 8 golf cart batteries (I would do 6 and see if I need more)
I am on the computer all the time, laptops are very power efficient. Use the power during the day to charge and use the laptop, then use the battery at night, if you are like me, I get about 6 hours from my MacBook Pro 2012, and then plug in after that if needed.
Get either a manual or automatic disconnect for the starter battery, so you don't have to worry about running the starting battery dead. And can (if you choose, charge the batteries with the alternator)
Use LED 12v lights, they are cheap (look on ebay) and all the rest of your power usage will be minimal.
I have a 2000w Xantrax Pure Sine wave inverter. I like it, the fan never runs and I leave it on all the time. Other brands are available of course, but it was cheap and works good for me.
On my camper, I only have room for 1 panel, and with it, I have 4 batteries. With this setup, I went all summer without running the generator once.
When we went hunting, we brought a chest freezer, with ice cream and meat etc. The single solar panel ran the freezer, computer, TV, charge phones, lights, water pumps, electric chain saw, dehydrator (<-- that sucker used a lot of power), and anything else 4 people spread out between my camper and a trailer (I ran a 12v cord to the trailer battery to hook them up) could use... for over a month. I didn't run the engine or generator AT ALL. I ran the freezer 4 to 5 hours a day, during the day. It was cold enough at night to be OK.
But, when I got an elk and we needed to get it frozen, there wasn't enough power to run the freezer all day and all night. So for 3 days I ran the generator (A Honda EU2000) it used 2 gallons of gas per 24 hours. Then put it away and the solar took over.
The Honda EU2000 will also run my A/C in the camper, I have only run it for about 4 hours at a time, And it didn't use a full tank (1 gallon) in that time. It will run any ~5000 BTU AC.
But the difference is I am not running an electric refrigeration system. It is propane, As is my heat, cooking, and hot water. So one panel is enough.
So, If one panel is enough to cover all my regular usage, and I know that one panel will cover the refrigerator (as it does on our boat) than I feel confidant in recommending this setup and feel it will serve you well.
If you need wiring diagrams or any other questions, I will be happy to help.
TL/DR I recommend 3 large grid tie panels (~1000 watts), 3 inexpensive MPPT controllers, 6-8 Lead Acid Golf Cart Batteries, system at 12v to simplify wiring, lights and hooking up to the alternator. An efficient 12v refrigerator, and a Honda EU2000 for backup and A/C use.