dkresto,
it depends on the quality of your beach, and how far you are willing to travel to find a decent beach with a steep slope. Skimming parrallel to the beach will not make a HUGE difference with a foamie, but if you ever come across good conditions you will wish you had one...

. In my opinion, one of the biggest differences experinced on a foamie vs a woodie is when you hit the deep and want to wrap around a wave. Foamies have superior float and speed. If your current skimboard is no good, maybe go for a larger more sturdy woodie for now. If you are really into the sport you will want to buy a foamie. A Zap comp texalium large was my first foamie and it was almost a year and a half before I got anywhere close to wrapping a wave. I still go the board (after 3 years), although it does't look as nice as it used to... Anyway my point is this, it takes time before you learn to get out into the deep and requires plenty of practice (but you have alot of fun in the meantime!) Once thing to note is this, foamies require a bit more maintanance than woodies. Often nasty rocks can do more damage to a foamie than to a woodie, and fixing resin and sometimes glass is not alot of fun. You can avoid this by staying away from rocky beaches obviously...but inevitably you will have to do some resin fixing (often not too much work). With good care a fomie board can last a long time.
I have orderd both my boards from skimcity.com. To buy a medium range board like my first one you would be looking at paying about $460-490 AUS (including postage), which is cheaper than what you can get at most surf shops. The price does depend on the AUS dollar. About used boards... I haven't come across any private sales. Skimcity sell second hand or repaired boards for a little less, but i reckon it is better to go for a new one.

. It all depends how keen you are to skim. A good woodie can cost up to $180, so its really up to you.
Cheers.