Dave i'm sure you are more than capable of assembling a system. You just need a parts list and a couple of hours. Building a PC is just like lego these days.
Yes, but it's just easier to pick and order everything from someone like this:
http://www.centrecom.com.au/catalog/build.php
Rather than buying this bit from here, this bit from there etc.
I suspect you won't save a huge amount by sourcing separately and building yourself?
It's been decades since I built my own PC.
Not really no. In Netherlands we are cheap, and have pricewatches. A couple of dozen shops update their prices daily for products, so we can find the best, place reviews etc. Unfortunately, all local market.
However, I do use it when putting together a new system. If you would order all parts at 1 'good' shop with reasonable prices, compared to getting cheapest everywhere (sometimes ordering at 4 or 5 shops).. it saves about <10% or so. E.g., on 600 euro's I can save about 50.
My experience with PC's these days is: it's very easy to assemble but not completely frustration free.
For example: I owned a Gigabyte motherboard once, which had such a crappy UEFI BIOS it wouldn't boot with certain USB devices plugged in (external harddrive) or a displayport monitor (I have to use DisplayPort for triple screen setups). Took me a week to figure out it's Gigabyte's crappy BIOS firmware.
RMA'ed the board (takes 1-2 weeks to process), had to seek replacement PC in the meantime, buy a different board, etc.
At that point I wish I just bought all the parts + 50 euro assembly + testing fee.
However, then the shop would need a computer case, harddrives, PSU, etc. I always reuse those parts, so I am not going to buy them twice..
Ah well, what I would do when assembling a new system now:
Intel i5 3570K or i7 3770K CPU. Note the 'K'. This is an unlocked CPU, ready for overclocking, and costs about 10$ - 15$ more. Moreover, it features a Intel HD4000 GPU over a HD2500 (in the non-K edition), which is faster with Quicksync video encoding.
So even on casual systems I'd spend 10$ extra for the much faster GPU. It may come in handy some day.
RAM: 16GB, 2 sticks of some sort. 1333/1600MHz DDR3 is good
Motherboard: recommend sticking with the major guys like Asus or MSI. I always have had trouble with other manufacturers.
SSD: Crucial m4, Samsung 840 series, Plextor M5P series, are all very fast and good drives. Get like 128G or maybe 256G (if you have big apps or games) as boot and Windows drive. Can't live without..
GPU: If you don't run games use the onboard Intel. It would probably outrun a low-end dedicated GPU..
HDD's/casing/power supply: reuse, buy whatever you like. Wouldn't cut on PSU's too much, as we all know how bad PSU's can get.