I've been quoted an eye-watering £1100

Obviously, that's not an option...
Seen them on the bay of fleas, but confused...the small ones only come in diesal and mine's a petrol engine. Something about needing an extra tank fitting.
My question is: if I can get one for a half-way reasonable price on ebay, will it be tricky to fit ie.can I get a local mechanic to do the job (no way will I be fitting it myself!)
Thanks,
Amanda