Help With Pivot For GridView

Hello, I have a query that works, it produces this:

UserID     UserName   GMC   Buick   Used
1                Jesse          1         2         1
2                Mark           4         3         2

But I need to pivot it, so that it appears this way

                  Jesse          Mark
GMC              1                4
Buick              2                3
Used              1                2

Here is my current query, I'm having a hard time with changing it to a pivot because I can't figure out what the aggregate function needs to be. 

declare @Param1 date = '12/1/2012',
@Param2 date = '12/31/2012'

Select Users.UserID, Users.UserName, [GMC] as GMC, [Buick] as Buick, [Used] as Used
From (Users
Left Outer JOIN
(SELECT UserName, Users.UserID, COUNT(Sales.Make) As GMC
FROM Sales
Join SalesUsers On Sales.SaleID = SalesUsers.SaleID
Join Users On SalesUsers.UserID = Users.UserID
WHERE (Sales.PreOwned = 0) And (Sales.Make = 'GMC') AND (Sales.SaleDate <= @Param2) and (Sales.SaleDate >= @Param1)
Group By UserName, Users.UserID)GMCCount
ON Users.UserID = GMCCount.UserID
Left Outer JOIN
(SELECT UserName, Users.UserID, COUNT(Sales.Make) As Buick
FROM Sales
Join SalesUsers On Sales.SaleID = SalesUsers.SaleID
Join Users On SalesUsers.UserID = Users.UserID
WHERE (Sales.PreOwned = 0) And (Sales.Make = 'Buick') AND (Sales.SaleDate <= @Param2) and (Sales.SaleDate >= @Param1)
Group By UserName, Users.UserID)BuickCount
ON Users.UserID = BuickCount.UserID
Left Outer JOIN
(SELECT UserName, Users.UserID, COUNT(Sales.Make) As Used
FROM Sales
Join SalesUsers On Sales.SaleID = SalesUsers.SaleID
Join Users On SalesUsers.UserID = Users.UserID
WHERE (Sales.PreOwned = 1) AND (Sales.SaleDate <= @Param2) and (Sales.SaleDate >= @Param1)
Group By UserName, Users.UserID)UsedCount
ON Users.UserID = UsedCount.UserID)