Hi Inf,
If you are in the US, you need to find a local repair shop that can do the services, if you cannot/don't want to do it yourself. Repair labour is $$$ for sure.
E34 is a nice car, with such high mileage. normal things will break if they have not been replaced in the last 50K miles. Plugs, hoses, water pump, fan belts, brake pads/rotors. Need to understand how to inspect the quality of these parts by physical inspection together with under chassis visual / under engine visual.
If there is an oil leak, then valve cover gasket is the minor issue but head gasket is major $$$. Engine internals are best left untouched as they cost a fair bit.
You need to be sure you really want to get into this. If not, just get a Ford or Chevy of around that price and you would probably spend less in repairs. If you are really lucky, you might be able to own this E34 for a good 2 years without much repair bill. But by then, the book value would be $2000 or less. Your choice.
In the US, if you wanted to get kits fitted, the labour is usually about the price of the items themselves. Painting them will cost extra. Ain't cheap, so be prepared for it. If you are DIY type, it can be a bonanza but you need the dedication and time to do it.