I'm not sure how either of these would work in a D&D type game. However, I have ran sneaky peaky / investigation games in my girls' face to face Call of Cathluhu / Delta Green mash up and my Traveller home brew game.

First, for the initial part of it (the initial recon etc) I have them do various skills to get info and these rolls represent hours to days worth of work. This helps them get important info (maps, blue prints, layout guard numbers rotation etc) . One thing that is critical is 'failing forward' . A filed roll still gets them the info (at least enough to make the plan) but it might alert the target someone is watching them, the party might have left a clue that points back to them etc. However, they always get the minimum info they need. On the other hand, a good success gets the info and they stay out of the sights of the target. A great success gets them extra important info (that floor plan they got from a normal success was for the most recent modification of the building, but the hard or extreme success get that AND the old original floor plan that shows where a room in the basement is that is missing from the newer floor plant / or shows an adjoining storm drain with a vent grate into the basement.

All of these checks can be any useful skill depending on how they want to get the info - a face man can charm a county clerk, a B&E expert can break into the county clerk's office, or the console cowboy can hack into the county records. Regardless they get the same data.

After that phase, (and this phase is optional and not always needed) they can do check on making things they know they are going to need, or get impritiant items (last adventure like this, they found out that the building they were breaking into had a high end comm blocker that fire walled all external comms and filtered all comms going into and out of the building. So, they would need something to hook into the building's antania or comm hub to allow them to use their inter team comms, and talk to the teammate on the outside of the building)

Then it is the phase of the actual event. Lots of skill rolls on stealth, deception, fast talk, charm  search etc (what ever game you use calls it). There should be a base target number for the difficulty, but it can be bumped up harder if there were some bad rolls in the first phase. Some of these can be base 'unopposed' rolls, some are against the opposing skills of the guards etc.

Oh yeah, some critical things to this:

The Traveller idea of task chains (one roll makes the following check in the task easier or harder based on its success or failure), This is great to making a lot of the tasks a team thign with 2 or 3 of the team working to get the task finished

The Call of Cathluhu 'Luck' (the basic check not spending luck, but if you include it that does make things interesting "I can spend a luck point now to avoid a bad roll in phase 1, but if we run out of luck in phase 3 we will be in trouble"). There is nothing like as they sneak into the building saying "ok give me a luck check" the looks on their face is ALWAYS near panic ...

A modified version of the Traveller Leadership skill (a check, anything they get above the TN of 8 is that many points the leader can hand out during that phase / a roll below 8 give me points to hand out as negatives).

I hope this is at least close to what you were looking at.