Alright so, a few updates.
The front frame panel thing (41338225982, don't think I mentioned the part number before). They sent me another one (no instruction on what to do with the first, bent frame), this time in a box. Now typically, a box is what I would expect for such an item, so I was initially relieved to see that they had engaged their brains. Unfortunately, the box was not sized even remotely appropriately for the frame. It wasn't wide enough, so the frame only fit inside when jammed in diagonally. The box was deep enough that the frame was otherwise free to bounce around inside. As a result, this frame ended up being even more bent than the previous one!
Fucking brilliant. So I message the seller again, asking to return both of the frames. They initially offer me half a refund in return for keeping the frames. What the hell am I going to do with two bent frames? Fine, they offer to take them back. So I request a return via eBay, and I get a Royal Mail label. I stuff both frames into the same box the second one came in (they're both munted anyway), stick the label on, and take it to the delivery office before work the next day.
Around lunchtime at work, I get a photo from my mum:
I laughed out loud! Fortunately, they had refunded me regardless, and eventually (like 2 weeks later), said I could just throw them away. So that is what I did v_v.
Jaded from the experience of ordering off-brand parts online now, I decided to just go down the OE(M) route. Looking online, a new frame would cost around £300, probably a bit more with shipping and taxes (only Danish and Italian companies seemed to be offering them online). I also called up the local BMW dealer, and much to my pleasant surprise, they were only asking £226. So I ordered it over the phone there and then. Now, it's quite a bit more than the £80 or so the eBay one cost, but at least I can be pretty damn sure this one will fit, and I get to collect it from the dealership myself, which I did, and it was surprisingly painless.
I waited about 15 minutes until the parts guy came out, just carrying the bare frame in his hands - no packaging or anything. While this may sound bad, it was actually quite releiving, because I was collecting it in my Volvo S40 (my E36 doesn't have folding rear seats, so the frame wouldn't fit), and there was every chance that the frame could've arrived on a pallet or something equally cumbersome.
The frame is now sitting in my dad's workshop until we have time to paint it.
A couple of other things I neglected to document...
I changed the transmission oil a couple of months ago or so. The car seems to be rather reluctant to go into 1st when stationary. It's not a huge issue, but can be rather annoying at traffic lights or so, and I've shoved it into reverse by accident a couple of times now. I replaced the oil with some Redline D4 ATF (even though it's a manual, it takes automatic transmission fluid), as that seemed to be generally what what people on the internet recommended. Of course, as always, reviews are mixed, but the balance was tipped towards that one, I think.
Anyway, that was a literal pain of a job on rough concrete floor. Having to drag myself to and from the underside of the car. It's rather messy even with a syringe thing, as the liquid is heavy enough to spill out despite the vacuum. One thing of note with this job, is to make sure that you can remove the inlet bolt before removing the drain bolt. Otherwise if you drain the fluid, then find that the inlet bolt is siezed, you're fucked. At least you're fucked until some penetrating fluid does its work (hours/days), or you have an impact wrench that doesn't just snap the bolt. Fortunately, I'm not speaking from experience, just passing on what I've read!
Unfortunately, the new ATF didn't help with 1st. But at least I have a bit more peace of mind. Maybe the synchro is just a bit tired, or the clutch is on its way out. Time will tell!
And finally, just today I changed the engine oil. I recently found that it's burning/leaking a bit - had to top up roughly 500ml a few weeks ago. But today I changed the whole thing. I gave it some Millers Oils EE Performance 10w-40 Fully Synthetic Engine Oil. Now, I have no idea what was in it before, but the engine certainly idles much nicer now - nowhere near as much rattling or ricketing. I read that these engines prefer slightly thicker oil (hence the 40), so maybe it previously had oil that was a tad too thin.
I'm still yet to replace the diff oil... Unfortunately, there's very little clearance between the fill bolt and the body of the car, so I'll need to get some specialised tool for it. That is if I can be bothered to get around to it before I put an LSD in or something lol.