The asbestos used for such things such as soffits, down-pipes, roofing and gutters etc. is comparitively harmless and you can take it down safely. However, there still are health risks (like falling off of the ladder). Usually guttering is held on by clips you can unclip by hand after you've scraped away the obligitary moss and build up of crap. Try not to break them, keep the lengths whole. There is often a bolt holding the sections of gutter together which are usually too rusted to undo with a spanner, you can eith cut it with a juniour hacksaw or bolt croppers, just advoid hitting the asbestos. if the clips are too old, corroded or knackered just cut straight through the metal fixings as these will have to be replaced anyway as the new plastic guttering is different dimensions (and so are the old fasioned cast iron guttering)
Once you've got the old guttering down (wear a breathing mask) just take it up the local municipal waste dump (but do not turn up in a van, just a car, or you'll be accused of being a trader and they'll refuse to let you dump it or charge you extortionate rates)and there should be an asbestos bin you can chuck it in, and occasionally there is a small charge for dumping asbestos (about a fiver). If you've got asbestos soffits (the bit between the fasia board and your wall) these are usually nailed up and are a bit more awkward but this reply is getting now.
Your tomatoes will be fine, your more likely to damage them if you let someone smoke around them or by dropping a big lump of the guttering on them!
if your not happy up a ladder or just not happy with dealing with asbestos full stop (though the asbestos used for guttering isn't going to harm you, especially on a one-off, or if you are hell bent on grinding it down to fine powder and sitting in an unventilated room chucking it in the air for a few hours a day, it might) get someone who is confident

hope that helps,

Yew Tree

Sorry, miss-read your message and wrote a moronic reply, your toms shall be fine

It is no more likely to do damage in the water than in the air.

If it is a modern garage it won't be asbestos. It will be a cement mix with a small amount of asbestos fibre acting as reinforcement:
http://www.aic.org.uk/FAQAC.html

About the site: You can paint over it with exterior paint. You can't walk on the roof safely though. You might use walk-boards if you want to do that. Use tar if the roof is poor. There isn't really a viable alternative for re-roofing.

I've walked on corrugated asbestos-reinforced roof many times. I'm not very heavy though :) They are quite brittle.

If you want to protect your rain water go to the web site below

Here is a link that might be useful: Gutter Mate