So, mine was an AV7 with internal seals. First time I did it, I put the seals in the case, crank bearings on the crank and chilled the crank in the freezer. I heated the bearing surfaces at the shoulder of the case. Seemed far enough from the seals to prevent heat damage. I ended up tearing one of the seals when I reassembled. Threads caught the rubber and I wasn't paying close enough attention.
Second time around, I placed the seals and bearings (heat case, chill bearings) first. I chilled the crank and fitted everything together. Since the crank is tapered, took a little bit of umph to slide it all together but the bearings in place helped guide the crank and prevent seal damage again.
I used some LucasOil assembly line on all the mating surfaces but you could probably use some 2-cycle oil as well.