Rob W;
Hi!
I have this beast in a shoe-box almost 95% done and nearing paint... NO, not a shelf-Q owing to some big issues, just that I wandered into some other immediate compulsions and it got laid aside for awhile... Actually seeing you and maybe some others bringing this one up may goose me enough to finish sooner!
OK - I'll start with I ain't no StuG expert! I have looked at many pics to sort of frame-up some visible details and possible add-ons - ID some visible stuff that I could easily change or improve. My sources include many Concord Military volumes with StuG pics, several works dealing with Pz III and StuG and variants, and, most rewarding, Gary Edmundson's "Modelling the S...G... III" Osprey Modelling #22. VERY nice detailed builds of a B and an F short-gun... LOT's of stuff for an earlier StuG build, here!
I think the CH E is a pretty nice kit - although not as detailed or as crisp in all particulars as later DML StuG kits (SmartKits and the like). This one is one of those CH orange re-box kits of an older DML 9000 series kit with added MagicTracks. It goes together well and seems to offer a solid basis for whatever enhancement you want. NO detail inside, so be aware with those hatches!
The things I thought most worth "improving": I detailed the road-wheels - the kit wheels are the older DML type without those pegs/brace-tubes and I added some

- probably most visible when looking at the spare wheels... I also detailed the outer wheel-face to show the welded form of the rim with its intermittent welds (easier to do than you think - take tiny segments of thinly-stretched sprue and weld them into that groove around the rim and texture a little with your knife-tip) - each outer wheel gets 6 - evenly-spaced around the rim. (OR... you could insert a new road-wheel set from a donor StuG or Pz III modern kit...

IF you want to go that route

)
I detailed the idlers a bit - they are slightly thick and clunky-looking in various places, and thinning the spokes gets them closer to the real thing (and to more-recent idlers...).
I also detailed my sprockets a little... wanted one to be a field-repaired item so welded on a patch-plate.
The hull-sponsons get added - these want some weld-seams. Also add weld-seams elsewhere around major metal joins on the hull - front plates-to-hull-sides, etc.
The "classic" DML III tow-cable on the rear deck wants improvement - I replaced mine with some cord and made brackets from sheet-styrene bits to replace that molded item.
I drilled pin-holes into all the visible hinge-ends around the hull - specially on the rear deck.
The head-lamps need some detailing. Adding clasps onto the cover-plate and a retaining hook to secure that plate when down (open) helps!
Adding tool-clamps and a few other small detail bits on the fenders helps a lot.
Adding the rear brace pieces under the fenders is visible and helps.
"Wire" those tail-lamps!
Open up those exhaust-pipes.
Detail the shock absorbers a little - they are visible.
I detailed the gun mantle a bit - added the bolts and washers on the back-side, etc.
Don't forget the small keeper-chains on the tow-pins!
I went around the hull and added and detailed eclectically following things I saw in Gary's Osprey builds. Stuff I could do using sheet styrene and stretched sprue scratch work. I found his nicely-photo'd build to be very inspirational (and rather intimidating

)
Hope this helps as a first starter to stoke your furnace a little! I'm sure that there are many many folks out there who can offer some additional and pointed guidance as you go. And some who will offer accuracy tips... Have fun and post some!
Cheers!
Bob
Now, like I suggested above... I think I'll go pull mine down for a gander!