Cart fix and shipping modifications for OSCommerce Site

We are running a small site that has been working well but last week our ongoing support sort of bailed on us. We are looking at several small projects but if this goes well would like to keep the freelancer on for ongoing support. Our oscommerce is running on CRE Loaded6 v6.2 B2B White Label[11]. We need the following for this bid however: 1) Fix Paypal Express Checkout (this option just disappeared from our site about week ago and we have no idea why). Module shows as installed, and it worked fine till last week. May be a simple matter of resetting a password or something should be a simple fix but we don't know what it is. 2) Googlecheckout mis-calculation of shipping costs. About 30% of the time a person is able to checkout with $1 shipping for no apparent reason. There must be a simple fix to this but agian we are no experts. 3) Simple script to enable us to disable Media Mail shipping for entire categories on our site. In looking around this has been addressed in other areas, we sell DVDs and CDs that are OK for USPS Media mail shipping but this is of course the cheapest option and people select it for other things like board games, costumes and other non-media options. We'd like to disable media mail as an option all together if the item is NOT in one of a certain category. 4) Paypal redirect back to site after a purchase (and googlecheckout)... very simple I'm sure. 5) Address capture required... people have been able to checkout on our site with NO shipping address disclosed on our site or in paypal, of course we have no idea where to ship and some of them don't even have an email address. We need to prevent this from happening. 6) General cleansing of the site. Through some poor initial programming it seems our EPB Import/Export don't work very well. The product ID is missing all together on this and so the import doesn't work at all. We also need to have our manufacturers cleared out as someone accidentally put in product codes for manufacturers on an EPB import and now there are over 1,800 of them. There is also something slightly wrong with our inventory, if you go to put a special on there are 3 or 4 of each item possible, although only one of each item shows up in our site. As I said this is a very small site and not a huge deal at all. the guy who set it up was learning as he went and got everything working but we could use some ongoing support so if the person doing this for us is reasonable and efficient we would love to give ongoing additional jobs including another site set up and other continuing projects to him/her. Let me state up front that I know next to nothing about OSCommerce or site programming. We just want our site to run. Right now its pretty crippled and sales are hurting due to the above issues.