I'm not sure what you chose - your title is 6.5 and your post is 6.8. There is nothing about those two that are similar and there is frankjly a lot of stupidity about which one is better - its like comparing candles to oranges.
Nope not at all ambitious, it's prudent. check out Hamlund Tactical NiB BCG - or you can run a phosphate coated one - there is no affect on performance, the former is just easier to clean.
When you torque on you muzzle device - make sure your barrel is in the vice and you aren't torquing the receiver - you will bend the barrel extension alignment pin (speaking from experience here). Also, ususally these are "timed" meaning they are oriented. If it has a crush washer, you'll be doing this for a bit until it's where you need it to be. It's an easy assembly