most split frame chassis arn't that difficult, I'm about to put a V2 with a decoder fitted on ebay you could visit
my old (5years old) and I stress old web site:
split frame chassis installation
I've done about 100 odd split frames so I have a bit of experience.
So how to tackle the V2
let see if we can talk you through it by memory !
normal method
remove the body, using two sharp knives gently remove the circlips on the centre drivers remove the rods
remove the base plate, remove the wheels, loosen the chassis screws, gently split the frame. I suggest you take a picture of the motion with a digital camera to help you with reassembly. Fit the decoder, it has to be quite small so I would suggest a TCS M1, Digitrax 123 or 143 I prefer them because they have a shrink wrap and cannot short on the chassis. From memory the decoder should fit inside the smoke box on the extreme front of the chassis. If it won't use a junior hacksaw and cut a slice off the top of the chassis, and then deburr your handy work, there is a photo on my web site on how to do this. The chassis is very soft and cuts easily. Throw away the copper springs and felt used to connect the motor to the chassis, I normally open out this area with the Dremel.
Right your decoder, cut two short lengths of shrink tube and place over the grey and orange wires that will go to the motor terminals. solder the wire to the terminals, and then cover you connection with shrink tube, use a heat source to shrink the tube over any bare wire and the terminals. The chassis haves, I always cut a path for the decoder wires so they don't get pinched on reassembly I used a dremel for this.
Reassembly. Before starting this use a small file and remove any burrs that could cause a short between the chassis halves. Use a Rose or counter sunk bit and lightly chamfer the pin location holes make sure the pins slide in them nicely, this greatly eases reassembly. Locate the motor and the drive gear, I always lightly lubricate with white grease, I have both woodlands grease and La Belle which is even better. Place the insulation pins in their half of the chassis, place the base plate locators in their splots and then bring the other half of the chassis to it and ease them together, it's not too difficult,
BREATH OUT once you have achieved this Make sure the decoder wires are not pinched, if your not sure repeat the exercise,
this is supposed to be fun now introduce the chassis screws and tighten but do not over tighten. A good knife and a screw driver helps is easing things together, it may look difficult but I've never fialed to reassemble one I promise you. Once the chassis is together then drop in the wheels note they only fit one way, reassemble the motion, and after turning the fly wheel to test everything is correct then fit the circlips. I find it better to reassemble on kitchen towel as it catches most small things "by magic". Now I havn't mention the catazzi assembly as I cannot remember it being a problem, obviously you will replace the brass current collectors on this section of the chassis and you solder the red and black decoder wires to this to collect the current.
You may need to lengthen or red and black wires to get to the end of the loco just join in a bit of wire and seal with heat shrink. locate the decoder with double sided tape or even blue tack but I prefer tape.
Now for the short cut method............... instead of removing the centre driver circlip rather remove the cylinders on each side and drop the motion and wheels out as one. Reassembly is much easier and there's nothing to brake. Use a precision screw driver (buy the 7 quid set at Focus it's quality) and the cyclinders can be eased out of the chassis, everything else remains the same of course.
Please let us know how you get on, most other split frames are similar, GWR types are much easier as the motion comes out as one.