So, to answer your question about hard points: the amount of hard points a weapon (or armor) has should be listed in its stat block with its damage, crit rating, encumbrance, and so on. Attachments are the items that you buy to put on the weapon to customize it, like adding damage or knockdown or the like. They don't require a check to add to the equipment item, unless specifically noted, and only take a few minutes to attach. Attachment modifications are the thing you need to make a check for. Modifications are something you do to customize the attachment even further, like adding a piece value to the damage attachment on your blaster rifle, although there is a chance of ruining the attachment in the process. The first modification on an attachment is a hard mechanics check that requires 100 credits worth of various parts, and the difficulty and cost increase for each subsequent modification to the same attachment.