Replacing a barrel in an AR isn’t difficult, but it does require some specialized tools and some knowledge.
What is the current barrel configuration? Barrel length and handguard type? Pinned front sight block or clamp on? Clamshell handguard or free float?
What is your desired end state? Free float or clamshell? Low profile block or front sight base?
Are you looking for match grade Precision or minute of man at 100yrds?