Tvheadend

There's no non-technical way of describing this... if by 'avoiding geekiness' you mean 'I don't want to understand anything about what I'm doing' then you're doomed.

The answer lies in how your NAS drive shares data onto the network. Windows uses something called SMB as a sharing protocol (versus NFS, which is the default Unix/Linux equivalent), so you need to look into how you could mount that share onto the OpenElec system.

Search around for how to use the mount command and how to create a startup script in OE. That - combined with the name/network address of the Windows box, and the name of the share that you're pushing onto the network - will tell you how to make the Windows share appear as a local directory on the OE system. Once it's connected like that, then the path you add to tvheadend is simply the the full name of that directory, starting at the root "/" (equivalent to C:\ on Windows).

That's telling me! OK - I understand although I don't see why XBMC provides me with a 'browse' facility but tvheadend does not.
Anyways - to the rub. So ASFAIK I have to mount the network drive on the openELEC system to provide a path address root. In order to do that I need a terminal, but openELEC does not apparently give that facility. So where to next?
I've just found this:
http://wiki.openelec.tv/index.php?title=Mounting_network_shares#OpenElec_.28.28pre.29Eden.2C_Frodo.29
Will that still work for Gotham?

Some further reading - it seems as though adding a NFS service on my NAS will make things easier for XBMC/TVheadend to access. Good idea?

The difference between XBMC and tvheadend in this instance is that XBMC has built-in NFS and SMB clients. What that means is that it knows how to browse a Windows or Linux network, see remote systems and access any shares they're pushing out onto the network. tvheadend (and, indeed, most things) doesn't have that code - it doesn't need it if you think about the purpose of the two applications. XBMC is inherently a "read things from disc, potentially a NAS" system so it's a useful feature; tvheadend is a "read things from tuners and relay it over the network and/or store it locally" system. XBMC also includes the code to make it OS-independent (e.g. Windows won't talk to NFS systems easily, yet XBMC on Windows can still do it).

Anyway, I digress a little.

Openelec does support terminal access - I think it's in the menu options, "enable ssh" or similar. That allows you to connect remotely from a different device (e.g. using Putty on Windows). Config can be messy if you're not Linux-experienced, in that the standard text editor is hardly user-friendly, but it's perfectly usable if you're diligent.

Regarding whether it makes much difference to XBMC... not really, but it certainly won't hurt. What you'd have is the remote directories mounted at an OS level so XBMC could see them as local locations instead of remote: it would see them as something like /home/fred/Videos instead of SMB://MyServer/shares/Videos. I've used both on OE and not seen any real difference to performance, so it's the toss of a coin, really - although you might as well use the mounts if you have them. What you'd probalby end up with is a local mount like /home/fred/NAS with sub-directories /home/fred/NAS/recordings (for tvheadend) and /home/fred/NAS/Films, /home/fred/NAS/TV Shows, /home/fred/NAS/Music, /home/fred/NAS/Music Videos and the like as XBMC sources. Whatever makes sense to you, though, as it doesn't really matter.

EDIT

Yes, that wiki page is probably still current, as it's an Openelec OS instruction rather than an XBMC Frodo/Gotham one, i.e. it's about commands that happen at boot time before XBMC gets loaded.