Firstly, if you have not seen it already have a read through this thread. You will find lots of good Sony information.
Unofficial Sony Alpha Thread
Next take a look at
www.dyxum.com there is a link at the top for lenses. You should find the Minolta one you have there and I think the kit lens is there as well. Members rate their lenses, this will give you some idea of peoples opinion of the lenses they have. Also check Ebay prices for the lens, this will give you an idea of how much people want them.
If you have both, then you could set the camera to manual and take the same pictures with both lens and on the same settings. I personally don't have a problem with the kit lens and have taken some good shots with it.
Apart from the few filters that have come with lenses I have bought all mine from Ebay, I get my UV's and CP's from this guy. They are cheap, but I have not noticed any obvious problems with pictures.
http://myworld.ebay.co.uk/photobitzltd I bought one ND grad, but it did look like someone had painted it by hand.
Lots of Sony users buy the f1.7 50mm prime lens, they go for between £50 & £80 on Ebay. Here is an example of one on Ebay, 190228756489 . It is a great lens for the money. Apart from the kits lens, I paid about £160.00 on Ebay for the other 3 lenses mentioned in my signature, you just need to be patient and think outside of the box when searching.