Great question. Adding this addition requires a really good, deep, compacted base. I would isolate it from the building by 1/2 inch, but if the base is good, rebar to the existing pad will help stop any displacement. You have to expect some settling, but the better the base, the smaller the amount. Web rebar won't help much, but 3/8 or 1/2 inch bar will hold the joint. The trick will be compact, wet, compact, wet. Make it rock hard. Good luck.
You don't need to concrete the whole thing.
You do need to shape it correctly. Even in arid areas (seems likely from the picture), water is the major thing that destroys poorly built roads - when it does rain, the water flows down the road and moves material - unless the road is shaped to divert water off to the side in a short distance, so that there is never so much water collectively running on the road that it moves the gravel. In a first step this might consist of adding water bars every once in a while to divert water to the side, but a complete solution consists of putting crown on the road, so that rather than having two wheel ruts (which become water channels, and then become deeper ruts) you have a slightly mounded profile and all water runs off to the sides (and, if need be, you have adequate ditches to handle the water once it is off the side of the road.)
Depending on finances and inclination, you can do this piecemeal over time for little cash with shovels and rakes and implements of destruction, or you can hire a contractor with a road grader. If the contractor also has a rubber-tired vibratory roller and knows how to use it, so much the better. You may want to remove (or break into smaller chunks) the random chunks of concrete, unless you are adding sufficient material to bury them. You will occasionally need to re-rake as your tires move material, but it should not be frequent or major if you drive calmly and are not spinning your tires. If you allow tire ruts to remain, and it rains, you'll have worse ruts after it rains. An old bedspring or section of chainlink fence can also be used as a maintenance drag (vehicle-pulled rake-equivalent) to help keep things where they should be.
If your gravel is 1" down to fines, it should work. If it's 1" stones with no fines, it won't pack well - good for drainage, not so good as a road surface. A gravel/stone supplier should be able to get you a few loads of "road base" which will have enough fines to pack.
If you work on it piecemeal, work from the top down, so each section you complete will stay put.
Best Answer
No, you can't resurface the surface economically, as it needs skill, and is a labor intensive business. You can repave, or adding topping concrete though. The original cement facing has simply flaked out due to weathering.