I'd recommend:
buying a bentley e30 manual https://www.amazon.com/BMW-E30-Service-Manual-1984/dp/0837616476/ref=sr_1_1?ie=UTF8&qid=1519082032&sr=8-1&keywords=bentley+e30+manual
Buying a decent mechanic tool set, I just bought a 450 piece one off sears for $250 but any good rated amazon one for $70-$120 should do for basic stuff
Register on a good e30 forum like r3vlimited.com and look at the diy guides and info there
The Bentley E30 manual is the best repair and maintenance resource for E30s, the electrical information is super helpful. However, it does not include the ix drivetrain, and a couple other things specific to the AWD model. For example, the engine bay layout is a little different, the battery is in the trunk, the driveshaft is reverse threaded (that was a frustrating weekend), oil pan and pump is unique, etc.
Most of it is the same as a 325is, just be aware that there are differences before you order parts and jump into repairs. So far it hasn't been anything critical and I've found plenty of information on forums like r3vlimited.
Here it is on Amazon but you can likely find it cheaper elsewhere. Probably lots used on r3vlimited and eBay. And if you didn’t know about the r3vlimited forums, definitely check it out. LOADS of info including DIY repair procedures.
https://www.amazon.com/dp/0837616476/ref=cm_sw_em_r_mt_dp_FKFA0MZFGBXF3KJKKX77
Everything you'll ever need to know
I didn't know too much when I started, but now I know that baby like the back of my hand!
Edit: Get the 6 cylinder. More is better, right?
definitely. I replaced a reverse light switch (screws into the transmission under the car) felt pretty awesome about myself. I would recommend getting the bentley manual. I understand that is the one to go with. Good luck!
All you'll ever need to fix an e30.
The e30 is an easy car to work on. There's plenty of space under the hood to work with. Its also very mechanical, so there's not a lot of computery things that can break. As somebody who owns a ~~moneypit~~ e30 I say go for it!
You should buy a copy from Amazon...
https://www.amazon.com/BMW-E30-Service-Manual-1984/dp/0837616476
Congrats! but... it doesn't actually have a lot of rust, right?
And Bentley for manual.
I'm working on a list of general E30 info. Feel free to message me about things that should be added!
FYI on Bentley - only 4 left!!!
I've only worked with one a handful of times. But each time I've had few issues. Just make sure you really research what you're doing, grab a bentley manual and follow its directions. Make sure you have a good set of jack and jack stands, the E30 is a relatively low car, so if you're doing work to it you'll need to lift it up sometimes.
Always do valve adjustments every 15,000 miles and the timing belt every 50,000, the M20B25 is an interference engine, if that belt goes it'll blow the entire thing. Make sure you change the oil and fluids, etc. etc. The engines in these things will go forever if you take care of them.
The cool thing about E30s is they're an enthusiasts car, so there's quite a few videos on YouTube on how to properly do a lot of this stuff, and there's at least 2 active forums; E30tech and r3vlimited so If you need to know how to do something chances are someone has already done it and can tell you how.
Not worked on an Eta. If they're similar to my engine then the head bolts are TTY, ie, single use. A Genuine replacement set can be had for $26.
https://www.ecstuning.com/BMW-E30-325i-M20_2.5L/Engine/Mechanical/ES18275/
As for places to buy parts:
Pelican Parts
BMA Parts
ECS Tuning
Turner Motorsport
FCP Euro
Autohaus AZ
Edit: just a note on the head bolts, don't by Victor Reinz. I did and found 2-3 were bent. Reading another website yesterday where someone found the same. ARP head studs are going to cost you about $220 for a set and (imo), aren't necessary unless you're going to strap a hair dryer to your engine (or intending to race your car). Also recommend Goetz brand for the head gasket (or Elring, or Genuine if you can afford it). +1 for buying the Bentley Service Manual