Don't waste your time/money on an expungement ... it won't work for immigration purposes.
You should meet with an attorney to discuss your convictions 48 months of probation indicates a very serious DUI conviction.
If you are low income go here: www.justice.gov/eoir/probono/states.htm or http://www.immigrationlawhelp.org/
1. apply to a school & get admitted
2. ask the school's foreign student adviser how to apply.
No, student isn't easier than tourist. A tourist only needs to show enough money to come and visit for a few months. A student needs to show $20,000+++ to cover their expenses for at-least the first year.
Why are you contacting us before you contact the school?
As for the H ... talk to the lawyer that did the papers ... you probably need an H visa stamp and need to wait until September 20 before you enter the US.