Your mower is over 12 years old right now and by the end of the mowing season it will excede 1000 hours. I doubt that your dealer would be able to go over your mower with a fine tooth comb and replace everything that was worn 50% for even close to what your wanting to spend.
From what your saying about just the elect parts would eat up a bunch of money. I think I would get it running and get a new mower. I know a bunch of guys here think getting a used mower even commercial is a good idea but to me your buying someone problems buying used. Of course you have gotten a few good years out of your mower so just cut your losses and try and find a good new mower that you can be happy with YMMV.