Do bonuses from magical weapons (i.e. +1...+5) add to the CMB when attacking? If, for example, the character has a +3 Glaive, does the +3 add in when the character is performing a Trip manuever?
Yes. Avoiding the specific example of "Trip" (which is controversial around here), in general yes they do.
Check page 199, left column, second paragraph.
Add any bonuses you have currently due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the manuever.
Magic enhancement bonuses on the weapon being used to perform the manuever used would qualify as 'other effects' in that sentence.
Trip.. has specific issues with it related to what weapon can be used. Discussion of that might derail your thread. Just a warning. :)