It seems from the Gemara 3b that the groom (or the grooms father according to Rashi end of 3b) should prepare 3 days for the wedding feast.
a) How much money should be spent on a wedding? Three days earnings? Enough food that it would take three days to cook?
b) Also, should the grooms father, as opposed to the bride's father, pay for the wedding?
a) I don't believe the Gemara was conveying how much money should be spent. It was probably an amount of time reasonable for preparations for the average wedding feast. As far as how much money should be spent on a wedding, one should consult his local orthodox Rabbi.
b) Regarding who should pay, there have been different customs throughout Jewish history. From the time of the Gemara until the time of the Rishonim and Shulchan Aruch, the groom's side was able to be Halachically forced to pay for a wedding meal which would be fit for the status of the groom and bride (see Tur and Shulchan Aruch E.H. 64:1). However, the custom then switched in many places to be the responsibility of the side of the bride, with some saying that the side of the bride can be forced to pay (Aruch Hashulchan E.H. 64:12). Nowadays, there are various customs in various places. It is therefore doubtful that either side can be forced to pay (see ha'Nisuin k'Hilchasam vol.2, 13:57). The best thing, obviously, is to work out the arrangements beforehand.
All the best,
Yaakov Montrose