1. Ok.

2. Not a good idea, the most reliable way is via Apps Market.

3. There is no big sense to insert the Upload file block to the Space View page because it will make a submit based on profile's data and will not "bound" the uploaded file to the current space if you want to have this effect.

LeonidS  I'm having the same problem with 'Files' module. I've not been able to install it on many occassions. finally, I decided to use phpMyAdmin to run the SQL script of 'Install.sql' and 'enable.sql' files.
running the 'Install.sql' script gives a repeated Warning: #1681 Integer display width is deprecated and will be removed in a future release. [this does not prevent the syntactic form running successfully]
on the other hand, when running the 'enable.sql' syntax I get the following error which prevents successful completion of the query:

INSERT INTO `sys_acl_matrix` (`IDLevel`, `IDAction`) VALUES

-- entry create

(@iStandard, @iIdActionEntryCreate),

(@iModerator, @iIdActionEntryCreate),

(@iAdministrator, @iIdActionEntryCreate),

(@iPremium, @iIdActionEntryCreate),

-- entry delete

(@iStandard, @iIdActionEntryDelete),

(@iModerator, @iIdActionEntryDelete),

(@iAdministrator, @iIdActionEntryDelete),

(@iPremium, @iIdActionEntryDelete),

-- entry view

(@iUnauthenticated, @iIdActionEntryView),

(@iAccount, @iIdActionEntryView),

(@iStandard, @iIdActionEntryView),

(@iUnconfirmed, @iIdActionEntryView),

(@iPending, @iIdActionEntryView),

(@iModerator, @iIdActionEntryView),

(@iAdministrator, @iIdActionEntryView),

(@iPremium, @iIdActionEntryView),

-- edit any entry

(@iModerator, @iIdActionEntryEditAny),

(@iAdministrator, @iIdActionEntryEditAny)

MySQL said: Documentation

#1062 - Duplicate entry '3-120' for key 'PRIMARY'