The physical job of changing the meter is not major. It'll take the engineer half an hour if he works slowly.
Any changes need to be initiated by whoever's name the meter is in (the landlord?). If you have no history of paying such bills, the supplier may not be willing to put it in your name unless you stick with the prepayment meter. If it was in your name, you would be responsible for the bills even though fairness suggests that the payments should be shared between you all.
You can't arrange to change to another provider unless the bills are in your name.
I would suggest that, if you feel that you are paying too much, you should ask the landlord for a copy of the last bill or, at least, try to work out how much you are paying by looking at the meter (there will be a charge per unit plus a charge per day). Sometimes prepayment meters are used to collect arrears and it is conceivable that you are paying for fuel used by previous tenants.