I will have to change the winshield on my 55S.
I have another one, used, which was cut out from the donor car with a wire. It has remains of the factory glue all around its perimeter.
The questions are:
1) How do I get rid of the old windsield without proper tools described in the original service manual (i.e. cutting wire and hollow needle)? I am thinking about axes and heavy hammers right now
2) It seems there are two schools of thought when it comes to removing the original factory glue. Theory One insists it must be removed without traces before applying the new glue, while Theory Two suggests it is better to use the old glue as a (sort of) primer, reasoning it will never be possible to repeat the factory technology, the old glue is factory-applied and thus it is better to put the new glue onto the beads of the old one.

Any input is gratefully appreciated.

Are they glued in in Mk1s? Never knew that, expected they'd be push fit like Cinqs....

The wire method makes much more sense. Less mess, danger of death, etc. You can buy the wire very cheaply on eBay or use piano/guitar string.

If the old glue is chopped back to the point where it is solidly attached, I see no problem, but beware of rust under the glue.

Over here the mobile screen fitters will usually do it for about £30.

The windshield had been replaced.
Tips:
Use a pair of twisted wires instead of only one.
The easies way to get through the old glue to separate the windshield from the body is a sharpened stripping knife and hammer.
There are two kinds of glass glues used - PU-based and MS-based. The old braids are PU-based and do not have to be removed, just cut them smooth with Stanley knife.