I'm pritty sure it's just a metter of plugging in the new ROM's to get it to work. Getting the machine to run smooth with 020 and OS3.9 will meen cutting back on most of the bells and whistles of OS3.9 though.
A quick way to increase the memory to 1M is to either install a 512Kb mem card and hack the motherboard (or if you have the later A500 motherboard simply solder the extra 512kb direktly to the motherboard and the hack), the hack is only a matter of cutting one line and soldering another so could be connected to a 2pol switch if you don't want to make the hack permanent.
