I'll answer number one, if I may.
A "RIP" is a "Raster Image Processor". It's a hardware and/or software (or combination) device which interprets PostScript language programs to produce a raster image specific to the output device. The dots on that hit the page, in other words.
Most RIP devices provide workflow options, so that a RIP operator can specify job options, such as which paper trays to pull from, whether or not to insert slipsheets, and if so, where, finishing options such as inline binding. Critically to your question, most RIPs also manage page signatures. That is, they can take a file organized into "Reader Spreads" and automatically reorginize the PostScript stream into "Printer Spreads", including changing the page size from 8.5x11 to 11x17 so that four pages print on a single sheet. This is as simple as, usually, clicking a single "checkbox" on the RIP.
Sometimes, it is advantageous to rearrange the file before it hits the RIP. This is easy to do with PDF files, since they are organized internally as a collection of objects. Changing the page order just means resequencing these objects.
A search at pdfstore.com:
shows several products that work as Acrobat Plug-ins for imposition. You could buy one and do your own imposition, sending your service bureau a file that is already organized in printer spreads.
These programs will also do your trims and bleeds.
3rd question: if the PDF is print-friendly (which these programs can also address through "preflighting"), it doesn't matter how it is delivered. Email, Web download, whatever. It's all good.
Thomas D. Greer
Providing PostScript & PDF
Training, Development & Consulting