You want my honest opinion? If you had place to do a backup, then try it, you could give it a go, but I don't think there is an official upgrade path set yet from DNN 2>> DNN4.
Your third party modules - you'd need to check they work in DNN4.
For me, I ended up redoing my DNN3.22 site from DNN2 as I tried for about 2 weeks to get it to work, but admittedly, I had some mods to the core tabs that interfered with the sql scripts from firing.
Depending on how much information you have in there, along with your time frame, sometimes a new slate is quicker to work with than trying to upgrade.
Just my opinion from someone who's done it in Feb and the whole experience was quite horrible, but I did have some self inflicted changes which I promised I will NEVER do again.
Your guy is correct in my opinion.
Nina Meiers