... I might be able to help. (We haven't 'seen' him in over 2 years.)
The answer to the 2nd question is to have the home inspected, and make this 'item' a Contingency Of Sale if you DON'T want to buy the house if it contains asbestos. (At least have the OPTION to decide on what to do put into the contract. You do have a Real Estate attorney, right?! Don't get me going on THAT one ...) If you have your 'concern' expressed in the Contingency Of Sale by your Attorney, then if the home has a 'good' inspection BUT the siding is asbestos, you can bag-out of the deal if YOU choose. This is why you want an Attorney writing this language. Or, easier yet, if the home owner answers YES to this question, then you'll have your answer, and can decide if you should go further. Make sure your inspector is an ASHI Inspector. And the reason you want an Attorney is because you want someone protecting YOUR interest. The bank has one protecting theirs, and they dabble in real estate every day!!! It's not that often you'll be spending $100,000 or so over 15 or 30 years, eh? And for a few hundred $$$, you should have someone who knows what they're doing watching your back. The same arguement goes for having a Home Inspector. Even with a brand-new home! (Enough said 'bout that. I can go on forever ...)
As to my answer to your first question, I say no. (Others may say otherwise but hear me out.) Assuming your Siding Manufacturer will warranty/guarantee the install over the asbestos shingles (even if exterior plywood or insulation board is put up first), AND XYZ years from now you're handed a Seller's Disclosure Form where you have to check YES to the question, "Does this house have any form of asbestos siding or roofing to the best of your knowledge?", good luck selling the house. The word asbestos freaks-out 99% of America no matter where it is and no matter how much you can placate them. I know it's a non-friable material, meaning that it's only a hazard if its 'dust' becomes airborne from, say, hitting it with a hammer or dropping it. I know that it's about 1% asbestos. I know that most jurisdictions will allow a homeowner to remove it themselves and have it hauled away in a dumpster w/o having to have the house bagged where men in white suits come in. I know you can simply wear a mask, gloves, long sleeve shirt, long pants and such, and remove the stuff w/o professional help. The problem is, I'm not your typical home buyer.
Assuming it's asbestos as I described (ie., it's non-friable, 1% asbestos.) Check with the local municipality to see if you are allowed to 'handle' it. The good news is chances are you can. And if you can, and you and your significant other want to save some $$$ on a siding job, you can do the demolition yourself. Just talk to your installer about what to do and how to dispose of it. (Be sure what's underneath the shingles BEFORE you go hammer-crazy. Schedule the timing of your demolition with the installer. Talk to him about that too. You'd want about 5 days of no rain, from start to finish. You don't want your house's walls exposed to rain w/o any protection.) I have a lot to say about this type of job so if you decide to go for it, get back to me and I can help. Here's a link that will say more so I'll stop for now. It's A Past Homeowner's Question About Asbestos Siding.