My old Microwave died. How would one remove this. It is Mounted above the stove. I noticed a casing arrould the Parameter; If I removed this casing. Would there be access to bolts holding the microwave?

Normal installation would be using a mounting plate attached to the wall. This is hung first, then the microwave is hooked onto the plate and then screwed from above to hold it in place.

Look for a couple of screws coming down from the cabinet above the microwave. Removing these will allow the oven to be tipped forward and out.
NOTE: IT WILL BE HEAVY. It is best a 2-person job, as it will probably want to come out on its own when you remove the second screw.

Here's more info: http://www.whirlpool.com/digitalassets/GH7208XRS/Installation%20Instruction_EN.pdf

And here's another helpful answer:
https://www.askmehelpdesk.com/appliances/whirlpool-microwave-removal-57917.html

Hope this helps,
WallyH

If it is not as mentioned above, you may try looking at the 4 corners for screws, on the front, they are not on the surface, you have to look in through venting or slots.

As noted above, 90% of over the range MW's are hung on a mounting plate behind the unit and then suspended from the cabinet above. Look for 2 screws and washers in the cabinet above the range, near the corners. If you see them, have someone support the MW, unscrew the hanger bolts and tilt out the MW. Install is reverse.

Couldn't find Installation Manual, Here are the parts layout if needed.
I see a wall template but no upper template which is used for locating the upper cabinet bolts. Since you said "Old", I thought this type may be a possibility.
Did you find screws/bolts coming down from the upper cabinet?

http://www.appliancepartspros.com/search.aspx?model=mh1150xm

Just checked the link and noticed "top mounting screws", you should have screws in cabinet.