Tip-offs never happen if you apex there directly from taking the mission. The die-roll for those sorts of mission wrinkles ("target fleeing" for assassination/takedown missions being another example) happens when you undock from the station/settlement in your ship.
If they do get tipped off though, don't worry. The mission doesn't update/activate until you're within 2.5km of the settlement. If you touch down outside that radius, before the mission update pops up on the screen and gives you your objectives, the settlement won't turn hostile. You can then disembark and dismiss your ship without it being fired upon.
Now, the next question is whether the settlement has patrolling ships or not. You'll have no trouble telling that from a decent distance away either. If there's no patrolling system defence/authority ships and the only traffic coming and going is trade ships, you're in the clear to use the SRV to approach. If there are patrol ships (usually at military settlements) then I leave the SRV in the ship and proceed to the settlement on foot. (though travelling 3km on foot might make you wish for an auto-walk feature)
Once you get close, your objectives will appear and the base will turn hostile, but there won't be any alarms yet. You can get well inside your SRV's sensor range of any base personnel before they spot you so don't worry about that. Just don't use the SRV guns. I usually park 500m or so from the base, in a ditch or behind a rock if I can swing it. Any closer and I really want an angle of approach with no windows and no staff walking around.
Speaking of which, be careful around windows, 'cause if someone spots you from one they'll immediately raise the alarm. The rooftops are rarely patrolled, but using your jetpack makes noise which might get people searching if you do it too close to them.
If you have an audio masked gun, especially something high-alpha like an executioner or intimidator, or even a tormentor, they really shine on these kinds of jobs. Try and get the drop on people and one-shot them. Grenades can be useful too, just lob them at whatever part of the base you want to draw attention to.
Learn your settlement layouts. Some of them have rarely-patrolled or even unguarded entrances to the building with the alarms in. Once you've got in there and disabled the alarms, it doesn't actually matter how much noise you make - some of my most successful settlement raids have just involved sitting next to the alarms panel with an unsilenced shotgun and blasting people as they trickle through the door one at a time.
Alternatively, there's plan B.
Plan B consists of a G5 dominator suit with extra ammo capacity (and three other mods of your choice) and two G5 L-6s with stowed reloading, magazine capacity, faster handling and whatever other mod you like, personally I go with reload speed in case I'm firing so many rockets that I end up reloading while my other launcher is still in the stowed loading delay.
Unless the enemy have some serious hardware (like enforcers of their own and a goliath) there's not a lot you'll encounter at a settlement that can withstand the kind of onslaught a loadout like that can dish out.
