Hi, I'm playing through this now and think I got spoiled earlier on the main plot. If I rush through that can I just play the rest of the game after without much change? (not like Fallout 3, like Skyrim) No spoilers please. thanks.

You can still do the side quests yet you'll be killing off the other factions. You choose who to side with over the course of the game, or you can string them all along for as long as possible. It's more like Fallout NV in structure.
But you can keep playing as long as you like after the main quest. Most of the stories are hidden in the different locations, it's all about exploration. I guess the only change will be that the eliminated factions don't show up anymore in random battles on the streets.

Thanks, I'll continue on as I have been then just in this knowledge. Not like some of the plot points haven't been hard to predict so far.

First you have to take it off that gun so first you build for the one you are taking it off the 'standard' part (so it costs nothing or little), that scope then will be in your inventory. If you can attached it to another gun, goto that gun and the part that you took off and it should say 'Attach' instead of build.

There are mods that unlock almost all the assets in the game.  People are using Institute pieces, for example.  They're also using other mods that let you do things like rotate your building objects.  I've used very few mods yet, myself, as I'm waiting for the GECK release.  A lot of the current mods will probably be redone in GECK and I don't want to go through removing and reinstalling.

Settlement mods made up most of the most downloaded until recently but people have figured out how to make a nude mod with a body-slider so now that and related clothing/armor mods are all the rage.

Power Armor is scattered around.  I have like 15 or so.  They're usually near or at: military checkpoints, pre-war crashed verti-birds, abandoned military vehicles, railroad boxcars, and sometimes those large metal containers.  Some are static, meaning it's always the same kind of armor, but others are dynamic and what you find depends on your level.  The X0-1 armor, which is the best, only spawns if you're like level 28 or higher, from what I've read, and probably only in the tougher areas of the map.  

SPOILERS!  Here are a few locations off the top of my head for super easy power armor pick-ups:  north-east of Tenpines Bluff in a railroad car; in the lake beside Covenant there is a suit underwater at the crashed verti-bird; a little east of Jamaica Plain in a small pond near a crashed verti-bird; up on the overpass near Grey Garden; and, easiest of them all, there is one near Sanctuary, a little ways north-east at a robot scrap-yard.

19 days later I completed the main story. All I could think after is 'Why does everyone want to kill everyone?' Where's the pacifist option? :P