Typically your looking at probably £300 I would have thought to have someone come out and strip this for you, so its worth attempting it yourself. Since your not bothered about making a clean job of it, I would have a go yourself.
The older models often take an age to strip down in terms of the base, however key principles of stripping the these models down is as follows:
1. Disconnect and cap off the gas, and make sure no gas is left in the burners.
2. First you need to get to the bolts securing the top on to the main body, this is done by removing the cover bolt head covers, most are screwed in some just clip but by in large you often end up damaging them so would normally need to buy them as spares, but since your scrapping you need not worry and just need to unscrew them, you could drill in reverse into them to free them, ive also been able to just use my thumb on them to unscrew them with a bit of WD40, it just depends how much crud is holding them in place.
3. Next you have 4 long bolts in each corner, they going through the top down, some have a socket head others have a square head the socket wrench goes straight on to. Once removed the lid should come clean away.
3. From there panels need to come off, the side and rear should come away as there just held in place by the lip of the top which has been removed, so no brackets securing them to the base of main body. The front however is often secured as that has alot of force being applied from the doors being open and closed, if you look on the side you will see the nuts holding the front on, my suggestion is use a viber saw or angle grinder, as most of the time these bolts have seized due to close proximity to the heat.
4. Next you need to hunt for the bolts coming out of the base plate, and again I would cut off the nuts should should normally be in a formation of pairs or groups of four holding each section in place.
Personally if you get to position where its not working I would just select an angle grinder, as you can spend a day just stripping it down, just make sure you use PPE as you have entire range of hazards from sharp objects to dust and debris to contend with.