Hi Markos, welcome to the best resource for e9's that I could ever think of. I appreciate your questions and have to say that the advice given below is well worth taking. If you want to rebuild a complete goner then this is the car for you; there are others who have done it with remarkable results but, BUT they knew exactly what they were up against. I do not mean to presume but if you are asking the price value of this car then it is probably not the right car for you. I think SF Don was being kind with his estimation, you could pay 10K for that car and never even miss it by the time you get it stripped down and start ordering parts. I think you will regret it. As a parts car I think the bumpers could be worth something, and I'm being serious, I don't see anything else that someone would buy. If you got the car for less than 1K, you could completely strip it down, salvage a few parts and in the process learn allot about the cars and their weak points making yourself familiar with the model. Other than that, I hate to say it but you could buy a 60K car and it would cost less than making that one a 20K car. For example, regarding the mold, it took me over 15 hours just to clean the trunk of an e9 I recently purchased that was infected with mold and there was barely any rust stains let alone rust on this particular car- see the thread "well I have to start somewhere".
Please keep visiting this site, ask lots of questions and wait for a "good" one to come up and jump on it. Since you are mechanical, wait for one with a blown engine or an auto trans that has given up the ghost but has a super body and interior. There is your bargain!!
Good luck!