If you got the rso/01 with the metal cab, the first hurtle is the largeplastic horn in the middle of the cab roof. All you can do is saw it off and do a lot of sanding.
As biggles2 noted, I remember some fit problems in the cab area. Nothing too big though.
The weakest part of the kit would be the tracks. They are stiff. I remember soaking them in hot tap water. Also, painting them can be a pain. I used a very light coat of Model Master Acrylic Gray (medium gray, I think) followed with a light drybrushing with silver. A little Rustall was also applied. To get a passable sag, I tied the tracks with clear fishing line.
I'm now working on the RSO/03 with an ambulance body for the Medic campaign. I've also done the Pakwagen version, but due to not being satified with it, I've posted no pictures.
I have another RSO/01 in the stash. It just may be one of my all time favorite kits.
Post some pics of yours. There are a few more on the site that are better than mine, but thank you for the kind words.
Chuck