If you can see a way to split the cooktop away from the oven and safely reconnect the gas it might be do-able. What I would do is turn the oven on high and check the temps at the rangetop. The oven vents through the rangetop toward the back of the unit so you need to be sure the part you cover with countertop isn't subjected to high heat.
The current rangetop acts as a metal cover with airspace over the oven...if you replace a portion of that with a flammable material like a countertop you may be creating a fire hazard. We have a wooden cutting board that fits over our stovetop so we can use it as counter space when not cooking, and with the oven on and baking, we have to remove that cutting board because it gets too hot.
One solution might be some sheet metal or other fire protection over the portion of the oven that you are replacing with countertop.
Proceed with caution, nothing will ruin your vacation like a trailer fire....
