Personally I wouldn't even bother with the L82, if you owned an LA1 (3400) that would be a better choice of engine.
I'm going to assume you're referring to the LX9 3500
As far as differences are.....the entire top of the engine (including heads) can be bolted down onto the older blocks, one will have get a hold of a throttle body adapter to bolt the LA1 throttle body to the LX9 intake as the LX9 makes use of wireless throttle.
The head gaskets differ minorly but the LA1 gaskets can be used with the LX9 block
The exhaust manifolds are completely different, you will have to use the larger LX9 manifolds & reconfigure your downpipe assembly.
That's about it for mechanical changes..........seeing as you want to use the L82 bottom end the ign firing will not be altered , the LX9 crank is not the same as the older L82/LA1
its been many many years since I did a 3100 top swap....
and yes, a large port 3100 or 3400 would be WAY easier (IIRC the only difference is the "3100 or 3400" cast into the manifolds or the minivan ones that are blank).
I know there is some nuance around what car is the best donor for the swap in regards to specifically the EGR being adapted. like Paul said 60*v6 is probably the best resource.
That all said, for all the work involved a whole 3400 swap would probably be just about as much work and cost not that much more if you can get a complete engine.