When replacing rear main seal has anyone encountered other major repair work? I am trying to avoid any surprises. Also I am taking to my local mechanic to do repair. Is this something I should have the volvo dealer do instead?

If your oil pan sealing is bad this is a good time to change it.
Don't know about cars with an automatic transmissions but in the end of the crankshaft is a small bearing that was the root cause why I pulled the transmission. It made an awful noise.
I also put in a new clutch/bearing and changed in/out shaft seals in the M47.
Should have done the seal for the gear lever but I missed that one so its leaking.
Great savings to do on this job if you do it yourself, Volvo quoted me +1200$.
It's not a difficult job though, any competent mechanic could do it.

Your local guy will do a fine job. When he does it, have him replace the front transmission seal as well, a ten minute addition to the job that will keep you from having to replace either for a long time.

I did mention this to him and he felt if everything was ok with the tranny he preferred not to disturb. Is the tranny seal the next thing to go? What is the life span on tranny seals? And in disturbing this area will this cause future problems? Please advise.

Thanks Ringlee