Unimog Club UK

Hi I’m in need of some wisdom please ?
Just acquiring a unimog but would like to make sure she’s good before hand so any advice on checks I should do she’s been sat for 6 years outside .
There are a few things I’d like to know also ?
Unimog 1985 u1300l diesel
1. Is this motor chain or belt drive ?
2. What oil does it use and how much ?
When I turn the key there’s a constant beeeeeeeeep which stays on when motor is running ?
3. Where is good to get spare parts from ? I’m in New Zealand .
4. Any advice on pre buying/test driving  tips and I’ve only done a short start is there anything that peeps would recommend doing ?
Many thanks David