ive come across a 1990 ZX2R ninja for sale, its said to be in good condition other than 'problem with second gear', price is $2000. this seems FAIRLY reasonable to me provided the bike is otherwise good. so im asking how hard is this to fix for a motorbike newbie? im a mechanic but have no experience working on bikes, im guesing its not as simple as separating the gearbox from the engine and replacing with a second hand one? is this a job a regualar mechanic can tackle, and even if i can, would it be cost effective? thanks in advance!