I replaced the fan switch myself on my previous Jenn air. I just looked at the manual, parts list, and found a parts place locally, bought the part and replaced the switch. You can likely find it online now. It was not difficult. I am sure now there is a you tube video guide back when I did it there was no such thing as you tube. So if I, of the female gender, can do it you can do it.

That ssaid if you were to have to replace that size in the future you will have the space to deal with in the cabinets and countertops. Make sure something is going to be available.

I just did a quick search, did not see any 47. Did see several 48 and a few 46. Rather expensive units at 48. But if you keep the current one you might consider leaving enough extra space to fit in a 48 use fillers that can be removed. You could have the granite cut back possibly or put some type of spacers between it and the current cooktop, I don't know if that would even be possible. Think of all the future issues!

I would assume it wouldn't be too hard to cut on site to a larger size in the future. If it's not induction though I would certainly replace it now though.

Does this JA have a downdraft? If so, replacing it with something that also ventilates is going be be challenging...

Learn from my experience. We remodeled the kitchen about 1 1/2 years ago. We kept all the old appliances, thinking we could replace them later, if we needed to. They were all working fine. I checked online to see if Thermador still made a downdraft. They do. It just isn't for a range, anymore. Something I missed. We have now replaced the refrigerator, dishwasher and last Friday the range. The previous range was in the peninsula with a downdraft. To replace it, we had one viable option, if we didn't want to add an overhead vent. I wish, now, that we had replaced all the appliances when we remodeled. It would have reduced the anxiety. They had to cut into our green iron soapstone for the new install. It all worked out, in the end, and I love the new range.

Oh, and prior to replacing all the these appliances, we had them fixed because each of them developed problems. I think that was the result of spending the summer in the garage. So, we ended up spending more money than if we had just replaced them during the remodel.

How old is it?

If it's more than 7 or 8 years old, you might be better off buying new and getting a standard size - probably 36".

Buy a 36". And engineer in a separate popup down draft. Or, much more functional, overhead venting. You have a dinosaur.

Skip the downdraft and get a real vent - your options will greatly increase.