For starters, using the "RN" block will open you up to a whole host of issues. The engine mounts are different, and you'll have to notch out the timing belt cover with a dremel to accommodate the 98-style accessories and serp belt. That is unless you switch over to 99+ style accessories too, which you'd have to source.
I've thought about it, and while I'd like to blame a lot of the issues I had with this project on the "RN" or 99+ style motor as opposed to an older HPT motor, truth is most of the headache had nothing to do with that. It's the little stuff - like having to completely re-do the fuel system, custom IC piping, new exhaust, swapping out wire harnesses, figuring out that you need different engine mounts, the list goes on - that really made it a pain. On paper it should all work out - the cars should be the same, or at least close enough to make it possible - that's what I thought, and that's where I found out it really wasn't true.
Don't get me wrong, it is absolutely possible to do a turbo swap and have it work out. For the 5 miles I had my turbo motor actually working before it overheated, it was a real rush hearing that turbo spooling up and feeling pinned back in my seat. That said don't expect it to be simple, cheap, or a fast job. Whatever you expect it to cost, multiply that number by 3 and then you'll get a more realistic number. However long you expect it to take, double that amount of time too.
If your son can afford to have this car off the road for a significant amount of time, and money is not an object, I say go for it. Doing a project like this is a great way to learn how to do pretty much any job on these cars that will ever need to get done, and a presents a good opportunity to freshen up other areas (suspension, etc) while the car is off the road anyways. That said, as the cost of these cars has come down so much in the past couple of years, it is MUCH more cost effective to find an 850 or 70-series turbo and start from there.
If you have specific questions you can PM me.
Cliff's Notes:- Don't do it.
- If you must do it, expect it to take much longer and cost 3X as much as you plan, and get ready for a world of frustration.