I reckon a full side is needed. Might as well replace the roof as well. Oh, and if you go that far you may as well replace the gutters too.
Sorry, being sarcastic now, not like me at all
Anyway, it really is case of asking yourself "How far do I want to go?"
You could spend several thousands of pounds and still not get a finished job. Or you could spend a few hundred and get a presentable job..... for a while. It really comes down to how much you can afford and how much, and how long, you want to keep your van. We can all invest loads of money in our vans and line the pockets of those who can do a great job, but can you afford to give someone your hard earned and still enjoy driving/ camping in the van? Let's face it: As long as it has an MOT and tax and insurance, and it's safe, you can enjoy it. The most important consideration for me is that it gets me there and it gets me back. I do not mean this post as an insult to anyone, whether they be the 'menders' or those who have been to a 'menders'. I just think that getting there and back without a breakdown is the most important part of owning a campervan.
This is just my opinion, please don't have a go at me.