Teardown specialist iFixit has already dissected a Mac mini barely a week after it launched. The 2014 model is found to be fairly easy to repair, but it would be difficult to do it yourself and you can forget about upgrading the processor if that's your sort of thing.
The version taken apart by the iFixit team was the entry level model, available from Apple for £399, with a 1.4GHz dual-core Intel Core i5 (Turbo Boost) processor and 4GB of RAM. It also contained a 500GB hard drive, on-board Intel HD graphics 5000, 802.11ac Wi-Fi and Bluetooth 4.0 connectivity.
One of the reasons given for the difficulty in repairing the unit at home is that, like with many Apple products, speciality screws are employed to secure the unit.
T6 Torx Security screws require specialist tools to remove, which makes it hard to clean the fan or replace the hard drive. And you can forget about replacing the processing chip as it is soldered to the logic board.
The 4GB of RAM is also soldered to the board, so you can't expand that either.
Of course, should it go wrong in the warranty period, Apple will repair or replace it, but essentially make sure you buy the correct model for your needs as it's unlikely you'll upgrade any of its elements after.
Apple has 2.6GHz and 2.8GHz versions available for £569 and £799 respectively.