PCBA question(s)

Hi guys’n’gals,

I have a few polarized components (0603 sized 10uF electrolytic capacitors) within my BOM. With thru-hole aluminum electrolytics it’s very easy to signify the correct orientation of the component as part of the silk screen. It’s not so easy with a tiny 0603 part. What method would Seeed like me to use to indicate this? (I’m hoping it’s as simple as including a ‘+’ character in the silkscreen next to the positive end?)
I’ve assumed that the Seeed PCBA process is a totally MANUAL process (i.e. it doesn’t use a ‘pick-and-place’ machine). Does Seeed have any requirements for component placement? eg: How closely together can I ‘squeeze’ 0402 and / or 0603 sized components in my layout?. (The OBVIOUS answer is to insert as much distance as possible between such components, but I’ve been trying to keep my PCB within the 10cm*10cm dimension). Are there any guidelines / recommendations you’d like me to work towards? Perhaps there are different ‘guidelines’ if two components are placed ‘side-by-side’ as opposed to ‘end-to-end’?
I suspect that at some point in future, Seeed might invest in a pick-and-place machine and solder paste printer. (That would be WAY cool!) If / when that happens, any guidelines / recommendations from 2a above might be tightened (or perhaps relaxed?).
Would it be ‘helpful’ to the Seeed PCBA team if I included a solder-paste stencil as part of my order (thereby allowing a ‘toaster-oven’ style reflow process as opposed to hand soldering every individual component pin). Perhaps the (currently US$70) cost of the stencil could be partially offset by having the ‘per-pin’ cost lowered from the existing US$0.10 to make this more ‘appealing’ to hobbyists? (I suspect it would save a decent chunk of time for the assembly team to ‘reflow’ PCBs rather than hand soldering - especially on devices like the 144-LQFP)