Electronic – Can a permanent marker be used on a PCB without damaging it

C: definitely the assembly shop, if you have the wallet for it. That's for you to decide. Ask some quotes, and decide if doing it yourself is worth the effort. Since this is a hobby project you may think your time is free, but then it has to stay fun as well, hasn't it?

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Just got this in a mailing from DesignSpark: fundraising may get you started to have it done by a shop. Erik raised 313 218 dollar for a 5 000 dollar target.
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Alternatively, B: Again, get a quote for a stencil. Yet, even applying the solder paste manually will take less time than hand soldering, which I would not recommend: the resistors and capacitors are not much of a problem, but the ICs may take quite some time if you want to do it proper, i.e. all pins soldered and no short-circuits.

Not A: it takes too long and it's messy. I would only do it myself if I could use the oven.

Remember that Jobs and the Woz also hand-assembled their first batch of Apple computers :-)

I've read @Matt's answer. The adhesive for holding the components during reflow is usually red in color, it's less runny, and there's usually less of it. Here's an example of such adhesive.

I've got a different hypothesis. I would guess that this is a thermally conductive adhesive that's holding something on the other side of the PCB. It may be improving the thermal conductivity between the PCB and the heat sink (or case). Notice that this white adhesive occurs mostly around components which are heat-sunk to the PCB.