Welcome to the board. Hopefully you lucked out and got one that had gone through a recent military reconditioning. It will make your life somewhat easier. There are a full set of military manuals specific to the SEE here
http://www.pirate4x4.com/tech/billavista/Mog/ don't bother to print them out as you will burn out a printer. It also may be worth taking a quick look at this collection of tech tips I assembled awhile back which are stored in the misc tech manuals of this site
http://www.steelsoldiers.com/showth...om-PS-Magazine-Maintenance-and-Operating-tips
As you will probably figure out, SEEs can have electrical woes. Many seemed to have ended up in Texas as one point in their lives and local rodents appear to like to eat the wiring harness. They seem to like to nest behind the dash and the damage is not obvious unless you start digging. The technical manuals do not have a wiring diagram. One of the members on this site did buy what may be the only set of them and graciously resold them to those who wanted them. If he has any left they would be on Ebay. Once confirmed that they are sold out others have offered to make a scanned version available but I haven't seen one to date. It is not 100% complete, there are some electrical systems that appear to have been added on after it left the factory floor. Hopefully you will not have to go through this but if you do let us know and we can point you in the right direction expect a lot of hours with multimeter and lot of head scratching
The best advice is that whoever sold you the SEE was portably clueless on what actually is and isn't working. Despite the low miles and hours, these have sat for many years and its questionable how good the maintenance was. There are known bugs and we are figuring them out as we go along. The manuals have an extensive section of maintenance and inspections and the best thing you can do is spend the time to go through them in its entirety. There is also a good operation manual that goes through how the systems are supposed to operate, take notes on what doesn't work the way the manual says.
If you think your SEE is going to be a runner out of the box with no need to go through systems you are in for potentially a lot of frustration. They are fundamentally 50 year old german tractors with road gear grafted onto them. The underlying components are pretty bulletproof if maintained but the various systems grafted on top of them are less so.