Step 1 - What you need and how to get it

Please check if your Ultimaker 2+ has been manufactured 2017 and later

You need 5 motor drivers, the latest UM2's, probably starting early 2017 miss the 5th driver. If this is the case you can try to get a board at an ultimaker reseller (very expensive) or get a chinese clone for about 75,- Be aware that you need to pay attention when using a clone board, it's been reported some have the connectors for LED's and fan's mounted up-side-down so CHECK THIS before installing.

Overview

Besides the stuff on Github, we're basically talking about two things: the second drive train (feeder, hotend, printhead parts, wiring) and some Mark2 specific parts.

Download the BOM from github. There are two sheets: a simple BOM and a detailed one. If you go for the option with the UM extrusion upgrade kit, you're most likely fine with the simple version. 

Drive train (feeder, hotend) 

Drive train option 1 - Ultimaker extrusion upgrade

By far the easiest option.
If you are starting with a UM2+, get one Extrusion Upgrade kit.If you are starting with a UM2 (non-plus) you might want to upgrade to the UM2+ at the same time, which requires two kits.

The kit includes some parts you won't need for Mark2 (shafts, but good to have these a spares, plastic printhead parts).

The extrusion upgrade currently costs € 395,- + tax.

Drive train option 2 - Bondtech

Get a Ultimaker 2 QR extruder upgrade kit 2.85/3.0 from Bondtech.
Same here, you might want to upgrade both feeders at the same time, which requires two kits.

This kit is currently € 144,20 + tax. The Bondtech kit however only includes the feeder and the parts required to mount it, which leads us to:

Drive train option 2 - continued

Search for a UM2+ print head at sources like aliexpress.

The important parts you want to use are:
the aluminum parts,
wire harness,
heater and temp sensor,
fan bracket and fans.

The hotend and nozzle might be crappy, so be prepared to replace it with a decent Olsson block or 3Dsolex hotend. You should find such a print head for around $ 85. In total, option 2 should cost around € 240,- (eventually plus another € 80 for a hotend).

Other feeder options

Of course you can use any other feeder which is suitable for the UM2. The detailed BOM lists some of them.

Mark2 Essentials

Magnets and screws

Magnets: You need at least 8 magnets of size 6 mm (diameter) x 3 mm (thickness), with a holding force of approx. 900 gr. It's a good idea to get some more. Metric sized magnets may be hard to source in some countries :P but we'll help you out. Then you will need some M3 screws and nuts. Find them listed in detail in the BOM.

Y-cables and cable extensions / Mark2 board

For connecting the 2nd printhead you have two choices:

• Get some Y-cables and cable extensions to extend the wire harness and connect directly to the board.
• Get the Mark2 extension board

(the picture shows my home made cable stuff not the one we will have manufactured ;)

Required and Recommended Tools

In addition the Essentials Kit and the required hardware, you will also need the following tools: The M3 hex wrench/allen key that came with your printer, or equivalent. It is the one used to adjust feeder tension, for example. A pair of pliers, a wrench or a driver set (M5.5) for loosening and tightening nuts. Some sandpaper to smooth the docking arm. A pair of pliers or vice grips can help with inserting nuts and magnets into printed parts if the holes are very tight. A hobby knife (e.g. Exacto knife) and small files are useful for cleaning up printed parts if necessary. A decent pair of tweezers is helpful for getting into tight places and precision placement.