Its not expensive at £950 delivered as long as it starts on its own battery and drives. If it was a Massey 165 or Ford 5000, similar size tractors of that era, then £2/3/ thousand for ruff machines. I did watch a ruff 995 in an auction last month make £1750. Also a tidy farm condition 1968 880 make £3000. If yours can be made tidy and serviced up, it should be worth £2000 all day.
I have a number of David Browns and a supporter of the brand, also a member of the DB Tractor Club which has a good web site, just like this one.
A 1968 would originally had shell type wings that are available and not hard to fit, doubt that it would have had a cab. It should have a chocolate brown engine and transmission with white tin work. Lights are a luxury on an old tractor and are easy damaged. I recommend a roll bar if it does not have one.
The transmission oil works the arms and has a filter underneath that requires changing every 500 hrs. The big down side of David Browns is that many farmers could not get their heads around the hydraulics. It is a big hydraulic computer, the operator 'selects' the system required, hence "Selectamatic". Good ploughing tractors, excellent traction and very low speeds.
They do need servicing and oils changing, but this is not hard or expensive on a DB. The best thing about DBs is the quality of the steel, they live outside and take some stick.
Let us know how you get on, or join the DBTC forum as there are plenty of 'fresh' owners on there from around the world.