Modern Vespa

Following on from this thread,
One day its a GT125, next day its a GT200 ???
I have decided to upgrade my X8 125 to 200 using existing head.
This is the same LEADER engine unit fitted to GT 125/200.
Im planning on photographing each stage for anyone elses benefit who may fancy a go at doing it themselves.
According to my research,it seems that the 125 unit is a derated 200 for the learner legal market with almost all components are the same.
I have a genuine piaggio 200 barrel/piston assy & genuine gasket kit.

A few questions....

1.Can I replace the barrel/piston while the engine unit is still in frame?
2.Will I have to adjust/replace any carb jets?
3.Will I need to fit a drive belt roller as per 200cc unit?
4.Will I need to adjust the ignition timing
5.Anything else I may have missed?

Your help will be much appreciated.

P.S. Please no comments on buying a bigger CC machine as I have looked into that and dont really want to coz I like my X8. ........And I like to "Tinker"..

Thanks very much...

Shaun..

Thanks very much to those who have PM'd me with advice.....much likey.. 8) 8)

Can anyone else offer advice?...or maybe a link or two.
Ive been studying past threads on this subject and have answered a few queries.

So im about ready to fit the 200cc barrel & piston and have come across a small problem.The ignition timing is different.
Will this make any difference?
If so,how can I alter the igntion timing?

Thanks